From June 3, passengers travelling with the US airline must check in 45 minutes before their departure time, regardless of whether they have a bag or not.

The airline's current policy requires passengers flying domestically to check in just 30 minutes prior to departure if they're not checking a bag.

Those on international flights must check in 60 minutes before departure and that rule will remain unchanged.

In a statement issued to The Independent, United said: "Starting June 3, our check-in cutoff time for domestic flights will change to 45 minutes before departure.

"The change brings greater consistency for our customers by aligning with our current checked baggage deadline and the check-in policies followed by most other airlines. Customers can review domestic and international airport check-in time limits and use our lobby kiosks for self-service as needed."

The company has not provided information on assisting with the rebooking process if a passenger fails to check in 45 minutes before departure, although several reports have indicated that people not checked into their flight at least 45 minutes ahead of take-off could be denied entry.

United's rule change comes at a time when the airline is under the microscope over flight safety - as the company faced criticism when two of its aircraft clipped each other at a California airport last month.

According to investigators, the incident occurred in a part of the airport where air traffic controllers do not communicate with flight crews.

United confirmed that nobody was hurt in the collision.