United Airlines has introduced a new mobile app feature that allows passengers who have been rebooked following a travel disruption to stand by for up to three earlier flights while keeping their existing confirmed reservation.

The airline said that the feature automatically monitors the selected flights for available seats, eliminating the need for passengers to repeatedly check the app. When a seat becomes available, United will send the customer a text notification, allowing them to decide whether to switch to the earlier flight.

Passengers can select up to three earlier flights through the United app and remain confirmed on their existing itinerary until they choose to make a change.

The feature is being introduced ahead of the busy Labor Day travel period. United expects more than 3.4 million customers to fly between September 3 and September 8, about 300,000 more than during the same period last year.

More than 85% of United customers use the airline’s mobile app on the day they travel, according to the company.

The new standby capability adds to United’s growing collection of self-service tools designed to help passengers manage disruptions without waiting to speak with an airline agent. The tools include automatic rebooking, meal and hotel vouchers for eligible customers and checked-bag tracking.

United also highlighted several other recent updates to its mobile app.

Passengers can now use Digital ID in Apple Wallet to make it easier to enroll in TSA PreCheck Touchless ID through the United app. The airline has also expanded its “Where is my plane coming from?” feature, which displays the inbound aircraft on the flight status page.

United recently became the first major U.S. airline to offer TSA security wait-time estimates at its U.S. hub airports, giving passengers information about expected security lines before arriving at the airport.

The airline has also added personalized connection assistance, including turn-by-turn directions to connecting gates, estimated walking times and real-time flight updates. Its ConnectionSaver technology can notify passengers when United is able to hold a departing flight for customers with especially tight connections.

For baggage, United has integrated Apple’s Share Item Location feature. Passengers traveling with an AirTag or other Find My network accessory can share the item’s location with United’s customer service team to assist in locating misplaced or mishandled luggage.

United said the new standby feature is intended to give passengers greater flexibility during disruptions while allowing them to retain their original confirmed reservation until they decide to accept an earlier flight.