Their termination, the sources said, threatens to undermine efforts to complete what is essentially an air traffic coordination system for space, currently operating in a trial phase as growing global demand for crucial satellite services sharply increases the number of spacecraft in Earth's orbit.

Transportation Sec. Sean Duffy called for increasing the pay for entry-level air traffic controllers this week.

Transportation Secretary Sean Duffy announced a new effort to boost the number of air traffic controllers in the U.S.