Yes, you can generally bring a backpack as a personal item, provided it fits completely under the seat in front of you. Most major airlines define "personal item" dimensions around 18 x 14 x 8 inches, though this varies by carrier (for example, United and Spirit have stricter limits). A standard "school-sized" backpack usually fits these criteria perfectly. However, if your backpack is a large 40L travel pack or is stuffed to capacity, a gate agent may require you to stow it in the overhead bin, potentially classifying it as your "carry-on" bag. If you are flying on a "Basic Economy" ticket that only allows a personal item, ensure the backpack is soft-sided so it can be squished into the sizer if necessary. It is a "pro-tip" to keep your most essential items—like your passport, medication, and headphones—in the front pocket of the backpack so you can reach them easily once you are settled in your seat.