A useful carry-on bag holds the items that would be hardest to manage without during the trip. Start with your route, the airline’s allowance and the possibility that a larger cabin bag might be checked at the gate.
Documents and arrival information
Keep your passport or required identification, boarding information and essential entry documents accessible. Save your accommodation address and onward-transport details offline. Keep a backup separately from the original documents.
Medication and personal necessities
Carry prescribed medication with identifying information and check destination restrictions before international travel. Include glasses or other essential personal items. Pack a change of clothing if a delayed checked bag would leave you without what you need.
Charging and entertainment
Pack compatible charging equipment and offline entertainment. Spare batteries and power banks belong in cabin baggage; remove them if a bag is gate-checked, as explained in the FAA baggage guidance. Check airline capacity limits and usage rules.
Comfort without a bulky collection
Choose a light layer and headphones if useful. Bring only the toiletries you need and check the applicable screening rules. The goal is a kit you can reach at your seat, not a second suitcase filled with every possible accessory.
For U.S. departures, consult the TSA item checker. Check the departure airport’s rules elsewhere; a limit from one country is not universal.
Organize for boarding
Separate the items you need at your seat from those that can stay overhead. Confirm under-seat and overhead dimensions with the airline. Keep aisles and exits clear, follow crew instructions and leave baggage behind if an evacuation is ordered.
Before leaving home, make one final check for documents, medication and the arrival address. These are more useful essentials than a long list of gadgets you may never unpack.