Michael Turner
Yes. A compact daypack will qualify as the complimentary under-seat bag only if its external dimensions do not exceed 18 x 14 x 8 inches (45 x 35 x 20 cm); pieces larger than that are treated as a full overhead carry and will generate a fee.
Measure the bag fully loaded (straps and exterior pockets included). Prefer soft-sided designs that compress under the seat. Keep liquids in a clear quart-sized bag, place a laptop or tablet in a thin sleeve for quick removal at security, and store bulky outerwear on top rather than inside the bag so the profile stays within limits.
Buy an overhead allowance during booking or via the airline app if your pack exceeds the stated dimensions–online purchases are usually cheaper than at the airport or gate. If you expect extra volume, check checked-bag fees ahead of time and compare total cost versus paying for an onboard carry.
Check the carrier’s official size rules and fee schedule within 24–48 hours before departure; published allowances can change. At the gate, present the bag under the seat in front of you to avoid surprises during boarding.
Is a rucksack allowed as the free under-seat bag on this airline?
Yes – a small rucksack qualifies for the airline’s under-seat allowance only if it fits 18 x 14 x 8 inches (45 x 35 x 20 cm); larger packs are treated as overhead cabin luggage and will trigger a fee.
Dimensions to follow: under-seat 18 x 14 x 8 in (45 x 35 x 20 cm); overhead carry-on limit 22 x 18 x 10 in (56 x 45 x 25 cm). There is no published weight cap for under-seat pieces, but the bag must be stowed beneath the seat in front of you.
Fee guidance: purchasing an overhead carry-on during booking typically costs less (commonly in the $30–$65 range depending on route and timing); buying at the gate is substantially higher (often $65+). Checked-bag charges vary by route and time of purchase; prepay online to save money.
Practical tips: measure your pack externally (including straps and pockets) before travel; remove rigid frames or bulky outer pockets to meet the 18 x 14 x 8 limit; place laptops in a slim sleeve rather than a padded compartment to reduce bulk; wear the pack through the gate if it barely exceeds limits (agents may still assess a fee).
At the gate and security: if agents determine the bag cannot fit under the seat, it will be assessed as an overhead carry and may be gate-checked or charged. Keep valuables, medications and documents in the under-seat piece to avoid loss or damage if gate-checked.
How to measure your rucksack to meet the 18×14×8 carry-on allowance
Measure the external dimensions exactly: 18 in (45.7 cm) × 14 in (35.6 cm) × 8 in (20.3 cm); include shoulder straps, top grab handle, wheels and any external pockets or attachments.
Tools required
Flexible tape measure (inches/cm), a rigid ruler for straight edges, a flat floor or table, and a piece of cardboard large enough to cut a box template.
Step-by-step measuring
Set the pack on a flat surface the way you would store it under a seat. Zip all compartments, fold or tuck straps into their stow positions, and position any removable pieces how you travel with them. Measure width across the widest external points (side-to-side) – this is the 18-inch dimension. Measure height from the highest external point (top of handle or highest zipper pull) down to the lowest external point – this is the 14-inch dimension. Measure depth from the front face to the back panel at the thickest point, including bump-outs or rigid pockets – this is the 8-inch dimension.
When measuring, press any soft fabric to its normal travel profile rather than fully compressed; bulging contents should be included. For wheeled models include wheel thickness and any fixed handle housings in the depth measurement. For cases with removable straps, measure in the configuration you will board with.
Create a cardboard box template sized 18×14×8, fold into a shallow box and attempt to fit the pack inside with its normal contents; anything that prevents the pack from fitting means a dimension exceeds the allowance. Airport sizers measure external size, so the template test replicates real checks.
If one dimension is marginally over (under ~0.5 in / 1.3 cm), remove or reposition external gear, tuck straps, empty outer pockets or swap to a slimmer carry companion. If over by more than ~0.5 in, choose a smaller model or transfer items to clothing to achieve compliant external measurements.
Which pack features (wheels, telescoping handles, external pockets) affect under-seat eligibility
Aim for recessed or removable wheels and a flush, stowed telescoping handle; exposed hardware and rigid frames are the most common reasons a small carry passes as a larger overhead bag.
Wheels and wheel placement
- Fixed protruding wheels typically add 1.5–3 inches to depth and almost always trigger overhead classification. If wheels are obvious on the exterior, expect gate agents to treat the sack as a standard carry-on.
- Recessed or inline-skate style wheels add about 0.5–1 inch and sit flatter; these give the best chance of fitting under a seat without appearing bulky.
- Four-spinner wheels increase overall footprint at each corner (up to ~2 inches each) and make under-seat stowage unlikely; two-wheel bottom rollers are preferable for under-seat use.
- Removable wheels (quick-detach) restore a low profile once detached; consider models where wheels can be unsnapped before boarding.
Telescoping handles, frames and external pockets
- Telescoping rods add 0.5–2 inches of rigid thickness even when collapsed unless they fully tuck into a dedicated compartment. If the handle housing protrudes, the bag will measure larger in the gate check.
- Internal frames or hard backplates prevent compression; soft-sided constructions compress by 0.5–1.5 inches in each axis and are more likely to meet under-seat allowances.
- External pockets that are non-flush or generously padded expand dimensions when filled. Flat zippered pockets are low-risk; bellows or cargo-style pockets can add 1–2 inches when used.
- Side water-bottle sleeves: empty and flattened sleeves compress nearly fully; leaving a bottle inside increases width/depth by ~1–2 inches and may push the bag over limits.
- Exposed straps, danglers or lash points should be tucked or secured; loose straps can catch on measuring templates and give the impression of extra size.
Quick pre-boarding checklist:
- Collapse and stow the telescoping handle fully into its compartment.
- Remove or detach wheels if possible; otherwise choose recessed-wheel models.
- Empty and flatten external pockets and side sleeves.
- Tuck shoulder straps into the back panel or a zippered strap pocket.
- Test fit under a standard seat or in a gate measurement box; if it won’t sit flat, consider using it as an overhead carry instead.
Packing techniques to keep a pack within the carrier’s 18×14×8 in under-seat limit
Aim for a maximum volume of ~33 liters and keep maximum depth under 8 inches; use soft-sided storage, compression, and flat-loading to preserve a low profile.
Use two compression methods: a small compression cube (~6–8 L) for 3–4 shirts compressing to ~2–3 in, and a medium sack (~10–15 L) for pants and a light jacket compressing to ~3–5 in. Place the medium sack at the centre to form a flat spine and the small cube above or below it to avoid a single bulky lump.
Flat-pack dress shirts and pants against the rear panel to reduce outward bulge; roll casual tees and technical base layers into tight cylinders and slot them along the sides to shave 0.5–1 in from overall depth. Thin merino or synthetic layers compress far better than cotton–swap one cotton tee for a merino equivalent and save ~1 in of thickness.
Keep rigid components flush: locate the laptop/tablet flat against the panel in a slim sleeve (0.5–0.8 in thickness). Replace clamshell cases with soft sleeves; a 13″ laptop in a 0.6 in sleeve typically adds less than 1 in overall depth. Position chargers and power banks in a slim zip pouch along the same plane to avoid stacked lumps.
Limit footwear to one low-profile pair; compress sneakers with a cloth wrap and fill cavities with socks and small items to retain shape without extra volume. Swap bulk boots for trail runners or sandals when possible–each shoe trade can reduce depth by 1–2 in.
Choose collapsible containers and travel-size toiletry kits: a 100 ml set in a 6×4 in clear pouch sits flush and prevents irregular bulges. Carry a collapsible water bottle that stows flat when empty; hard bottles create irreversible depth increases.
Tuck straps, buckles and removable harness pieces inside the main compartment or into an internal pocket. Flatten shoulder straps and secure them with a small elastic band so they don’t protrude. Remove non-structural frames or stiff inserts to gain 0.5–1 in across the board.
Final compliance check: build a cardboard box template at 18×14×8 in, load the gear as packed and close the flaps. Measure the maximum depth at several points; if any point exceeds 8 in, swap the bulkiest single item for a lighter alternative, move that item to wear-on-board, or re-compress the affected cube until the template closes flat.
What happens if your rucksack exceeds the 18×14×8 allowance: fees and gate-check options
Immediate action: pay for an overhead-cabin allowance before you reach the gate – online rates typically run $30–$65, counter rates $40–$85, gate rates $100–$150. Purchasing early avoids the highest surcharge.
At check-in or boarding: gate agents will measure; if the bag is too large they will require a paid upgrade or will gate-check the item. Gate-checking usually involves a tag, placement in the aircraft hold, and retrieval either at the aircraft door or at baggage claim, depending on the carrier and airport.
Typical fee ranges (industry averages): overhead-cabin purchase: $30–$65 online, $40–$85 at counter, $100–$150 at gate; checked luggage: $30–$45 prepay, $40–$70 at airport; oversize/overweight surcharges: $75–$200 depending on pounds and linear dimensions. Consult the carrier’s published fee table for exact amounts.
If you’re asked to gate-check: remove electronics, medications, travel documents, valuables and fragile items and keep them in a smaller under-seat bag. Keep the gate-check stub and photograph the tag and condition of the bag before handing it over; evidence speeds any damage or loss claim.
Options to avoid fees at the gate: transfer heavy or bulky contents into a coat or companion’s bag, wear bulkier clothing, consolidate into a purchased overhead allowance via app, or check the bag curbside at drop-off where checked-luggage rates can be lower than gate surcharges.
Liability and claims: documented damage or loss must be reported at the airport before leaving the terminal if possible; retain receipts, boarding pass and photos. Typical carrier liability for checked/gate-checked fabric bags is limited – filing windows are short and reimbursement often caps at a fixed amount per passenger.
After repacking or washing a fabric rucksack, use a gentle homemade scrubber for spot-cleaning – see how to make natural scrubber for a safe DIY option.
Carry a soft-sided daypack no larger than 18×14×8 in (45×35×20 cm); examples below that commonly fit beneath the forward seat and avoid an extra fee.
Choose compressible, soft fabrics and slim profiles – models and types listed here meet typical under‑seat limits or are very close when empty.
| Type / Model | Approx. external size (in / cm) | Construction | Fits under forward seat? | Notes |
|---|---|---|---|---|
| Osprey Daylite (small daypack) | 18 × 10 × 8 in / 46 × 25 × 20 cm | Soft nylon | Yes (compressible) | Designed for a 13″ laptop or light camera kit; straps tuck down for stowage. |
| Herschel Pop Quiz (compact commuter) | 17 × 11 × 5 in / 43 × 28 × 13 cm | Soft canvas/poly blend | Yes | Flat profile and padded sleeve; ideal for documents and a slim laptop. |
| Peak Design Everyday Sling 6L (sling) | 12 × 8 × 6 in / 30 × 20 × 15 cm | Soft, padded | Yes | Small, easily stows under a seat or inside a larger carry; great for camera gear. |
| Timbuk2 Classic Messenger – Small | 14 × 11 × 4 in / 36 × 28 × 10 cm | Soft fabric, flap closure | Yes | Shoulder/crossbody profile keeps bulk low for under‑seat placement. |
| Patagonia Atom Sling (8L) | 14 × 8 × 4 in / 36 × 20 × 10 cm | Soft, low‑volume | Yes | Single strap, quick access; minimal bulking when packed with soft items. |
| Foldable duffel (Ultra‑compressible) | Up to 18 × 14 × 8 in / 45 × 35 × 20 cm | Ultra‑thin ripstop nylon | Yes (when not overstuffed) | Can be flattened or folded into itself; useful as a secondary under‑seat carry. |
| Slim laptop sleeve with strap | 15 × 11 × 2 in / 38 × 28 × 5 cm | Soft padded fabric | Yes | Lowest‑profile option for tech gear; slips under a seat or into larger cabin bags. |
| Small camera cube inside a soft daypack | Varies; typical outer pack 16 × 12 × 7 in / 41 × 30 × 18 cm | Soft outer, padded insert | Yes | Provides lens protection while keeping overall thickness low. |
| Hard‑shell mini roller (wheels & telescoping handle) | 18 × 14 × 8 in / 45 × 35 × 20 cm | Rigid | Usually no | Wheels and fixed handles often prevent true under‑seat stowage despite matching dimensions. |
If a pack measures at or under 18×14×8 in and is soft‑sided, it will generally be accepted for under‑seat carriage; rigid small rollers and heavily structured cases are the most common rejects. Check external measurements with straps tucked and pockets empty before boarding.
Exceptions and special cases: diaper bags, medical equipment, and the carrier’s allowances
Bring infant diaper kits and medically necessary devices separately from paid carry allowances; most carriers allow them in addition to the free under‑seat bag when they meet documentation and safety rules.
Diaper bags: what is allowed and how to handle them
- Allowance: One diaper bag per passenger with an infant is generally allowed in addition to the free under‑seat allowance. Expect agents to place it under the seat or gate‑check it if oversized.
- Recommended maximum for under‑seat stowage: keep external dimensions close to 18×14×8 inches to avoid gate‑check delays.
- Packing tips: keep diapers, wipes, bottles and a change of clothes in the top compartment for quick inspection; secure liquids in clear bags for TSA screening (medicinal baby formula and breast milk follow TSA exceptions).
- Labeling: affix a luggage tag with name and infant’s age; carry proof of infant age if traveling internationally or when asked.
- Small crossbody alternative: see best messenger bag for concealed carry for compact options that fit under the seat.
Medical equipment: documentation, batteries, and pre-notification
- Types usually exempt from carry‑fees: wheelchairs, walkers, prosthetics, oxygen concentrators (POCs) and other mobility or life‑support devices are typically accepted in addition to the standard cabin allowance.
- Advance notice: contact the carrier 48–72 hours before departure for POCs, compressed oxygen, powered mobility devices or anything requiring special handling; many airlines require written medical approval for POCs.
- Battery rules: lithium‑ion batteries ≤100 Wh are permitted in the cabin without approval; batteries >100 Wh and ≤160 Wh require airline approval; >160 Wh are prohibited. Spare lithium batteries must travel in the cabin with terminals protected.
- CPAP and other medical devices: bring prescriptions or physician letters; carry devices onboard when possible and bring backup power sources compliant with FAA limits.
- Medications and liquids: medically necessary liquids over 3.4 oz are allowed through security but must be declared for inspection and kept accessible. Carry prescriptions or a doctor’s note for controlled substances.
- Gate‑check vs checked: manual wheelchairs and mobility aids are usually gate‑checked free of charge; battery‑powered aids may require special handling and can sometimes incur handling procedures but not standard checked‑bag fees.
- At the gate: notify agents about any fragile medical gear that cannot be checked; request a tagging for fragile handling and, if needed, ask for a supervisor to confirm accommodations.
