• must fit under your seat or in the overhead bin;
• should not be more than 9 x 14 x 22 in. (23 x 35 x 56 cm) (length x width x height) or 45 linear inches* (114 linear cm); and
• may be required to travel as checked baggage if the bag cannot be safely stowed on a particular flight.
  

*linear measurement = length + width + height

United exempts the following personal items from your one bag and one personal item limit:

• Child safety seats for ticketed children
• Assistive devices (canes, crutches, etc.)
• Outer garments (coats, hats, etc.)

Liquids, gels and aerosols
Liquids, gels and/or aerosols are permitted through security checkpoints worldwide. Items must fit in one clear, resealable quart- or liter-sized plastic bag, in containers of 3 oz. (100 mL) or less. (For ease of memory, please follow the 3-1-1 rule.)

Plastic bags must be completely sealed and will be x-rayed separately at the security checkpoint.

The following items are allowed but must be presented to officials at security checkpoints if they are of greater volume than 3 oz. (100 mL):

• Baby formula/milk, including breast milk and baby food in containers. You do not have to be traveling with a baby or small child for these items to be allowed.
• Medications (liquid, gel or aerosol)
• Liquids, juices or gels for diabetic passengers who indicate a need for such items to address their medical condition. (A letter from your physician is not necessary.)

Flights departing from or connecting through the United Kingdom
If you are departing from or connecting through London Heathrow (LHR), you are allowed one carry-on bag and one personal item as stated above; however, please note that the Department for Transport (DfT) regulations in the U.K. require that the 45 linear inches (114 linear cm) includes the handles and wheels of your carry-on bag.

Additional information
For additional information about carry-on guidelines, visit the TSA's website at www.tsa.gov.