One personal item for every US airline: what fits United, JetBlue, American, Frontier and Allegiant
Five US airlines in our list publish a personal-item size, and they don’t agree. A bag that fits under the seat on Frontier can be too wide for United. Of the 1,902 bags in our catalog, 188 fit all five. Most are slings; only 34 are backpacks, and the largest holds 22 litres.
If you skip United, the picture changes: 396 bags fit the other four, including 191 backpacks of up to 32 litres.
The five sizes
| Airline | Personal-item size | Bags that fit | Cabin bag on the cheapest fare? |
|---|---|---|---|
| Frontier | 46 x 36 x 20 cm (18 x 14 x 8 in) | 659 | No, unless your bundle includes it |
| American | 45 x 35 x 20 cm (18 x 14 x 8 in) | 544 | Yes |
| Allegiant | 45 x 35 x 20 cm (18 x 14 x 8 in) | 544 | No, it is paid |
| JetBlue | 43 x 33 x 20 cm (17 x 13 x 8 in) | 396 | Yes, on all fares |
| United | 43 x 25 x 22 cm (17 x 10 x 9 in) | 190 | Not on Basic Economy, except to South America and across the Atlantic or Pacific |
Delta, Southwest and Alaska don’t publish a personal-item size on the baggage pages we use.
The last column is the reason the personal item matters. On Frontier and Allegiant, and on United Basic Economy for most domestic trips, the personal item is the only free bag. On American and JetBlue, it is the second bag next to a full carry-on.
United’s width is the problem
United’s personal item is the narrowest: 25 cm (10 in) wide, where the others allow 33 to 36 cm. Among the 396 bags that fit the other four airlines, 208 fail United, and every one of them fails on width alone. Half of our backpacks of 30 litres or less are between 27.9 and 31 cm wide, which works on Frontier and American and not on United.
United is more generous on depth, 22 cm against 20 for the others. That rarely helps: the 76 backpacks narrow enough for United are 16.75 cm deep at the median.
Backpacks that fit all five
| Backpack | Volume | Weight | Size (cm) | US price |
|---|---|---|---|---|
| Eastpak Tecum Cabin CNNCT | 22 L | 0.80 kg | 39.9 x 24.9 x 19.8 | $120 |
| Gossamer Gear Elixir 20 | 20 L | 0.18 kg | 42.5 x 21 x 15 | $225 |
| Mystery Ranch In and Out 18 | 17.9 L | 0.30 kg | 39 x 23 x 20 | $89 |
| Eagle Creek Packable Backpack | 16 L | 0.16 kg | 43 x 23 x 13 | $59 |
| Osprey Daylite Cinch | 15 L | 0.34 kg | 41 x 24 x 19 | $60 |
| Waterfly TransformerX 4.0 UltraLight 15L | 15 L | 0.19 kg | 40.6 x 24.1 x 15.2 | $19.99 |
The Eastpak Tecum Cabin CNNCT is the one to look at first: at 24.9 cm wide it slips under United’s limit and still takes a 16-inch laptop. Several of the others are packable daypacks that fold into their own pocket, light but with little structure.
For a sling, the Boundary Supply Errant Sling (15 L) and the Aer Sling Bag 3 (13.5 L) are the largest that fit all five.
If you don’t fly United Basic Economy
JetBlue’s 43 x 33 x 20 cm becomes the strictest size, and the choice widens a lot:
| Backpack | Volume | Weight | Size (cm) | Laptop | US price |
|---|---|---|---|---|---|
| JanSport Main Campus | 32 L | 0.60 kg | 43 x 32 x 17 | 15” | $62 |
| WANDRD PRVKE Zip 31L | 31 L | 1.31 kg | 42 x 30 x 15 | 16” | $254 |
| Osprey Sojourn Porter 30L | 30 L | 1.40 kg | 43 x 33 x 20 | n/a | $180 |
| Cabin Zero Classic Backpack 28L | 28 L | 0.60 kg | 39 x 30 x 20 | 15.6” | $92 |
| Cabin Zero Military Backpack 28L | 28 L | 0.90 kg | 43 x 30 x 16 | 15.6” | $125 |
| Osprey Daylite Expandable Travel Pack 26+6 | 26 L | 0.80 kg | 43 x 33 x 15 | n/a | $110 |
A 28 to 32 litre bag is enough for a long weekend, and these fit under the seat on Frontier, American, Allegiant and JetBlue. That means you can fly Frontier or Allegiant on their base fare with no bag fee and still carry a real travel bag. Check the depth after packing: several of these are exactly 20 cm deep on paper.
How we counted
Sizes come from each airline’s own baggage page, linked on its airline page, checked in September and October 2026. A bag fits when its published dimensions are within the limit in any orientation. Inches are rounded from the centimetre figures. None of the five airlines publishes a weight limit for the personal item on the pages we use.