In an effort to speed up the boarding process, Delta Air Lines is expanding a service to load passengers’ carry-on bags for them.

The complimentary service called Early Valet will be offered on only a small fraction of Delta’s flights. For flights with the service, the gate agent will make an announcement to passengers. Once flight crews are on the plane and before general boarding starts, an airport customer service employee will take the bag onto the plane and stow it above the customer’s assigned seat.

Delta spokesman Morgan Durrant said the airport customer service employees who stow the bags for passengers will politely decline tips.

The service will be available mainly on aircraft such as the Boeing 757 and Boeing 737-900, long single-aisle planes with a lengthy boarding process, according to Durrant.

Delta offered the service in Atlanta on a trial basis last year, and on June 1 began expanding it to more hubs for the summer. By mid-June the airline plans to offer Early Valet service about 200 flights a day across its system, out of more than 5,400 daily flights it operates.