Will it fit a 15-inch laptop?

No. The sleeve is sized for 14-inch laptops, and a 15-inch machine will be tight or won't fit. Look at Tumi's larger models for 15- and 16-inch laptops.

Is it good for air travel as a personal item?

Yes. Its compact size makes it easy to slide under an airplane seat, though it holds less than a dedicated travel backpack.

Does it have a luggage pass-through?

Some versions include a trolley strap and others don't, so check the specific model before buying if you plan to stack it on a suitcase.

The shell resists light rain and splashes, but it is not fully waterproof. Use a rain cover in heavy downpours.

How does it compare with larger Tumi backpacks?

It is lighter and more compact but gives up capacity, extra pockets and sometimes the luggage strap. Choose it if you carry little; choose a larger model if you need room for gym gear or overnight items.