(Reuters) -Southwest Airlines has recalled 209 pilots from a voluntary extended leave program to support its summer schedule, the company said on Monday, as airlines prepare for a recovery in demand as more Americans receive COVID-19 vaccines.

The pilots will return to active status on June 1 and will then complete all of the necessary requalification training requirements before they fly with passengers.

Among other major U.S. carriers, Delta Air Lines and American Airlines have also recalled pilots who were sidelined during the pandemic.

United Airlines, which reached a deal with its union to keep pilots active throughout the downturn, said last week it was preparing to hire about 300 pilots as travel demand rebounds.

Low-cost airlines have also recalled pilots and are hiring again.

(Reporting by Tracy Rucinski; Editing by Leslie Adler and Howard Goller)