Air traffic controllers are essential to commercial air travel, but shortages are something pilots have faced before.

Flights were temporarily grounded at Los Angeles International Airport on Sunday after an FAA-reported equipment outage. The disruption adds to ongoing US air travel delays caused by staffing shortages during the government shutdown and comes weeks after a cyberattack hit major European airports.

Travelers within the U.S. could experience flight delays as weather problems, air traffic controller shortages persist.

How do our skies work? Three levels of air traffic control at major airports. A local tower where controllers guide planes using technology, experience and their eyes to watch up to a certain altitude. Anything above that is handled by remote facilities. A bulk of our public airports don’t have local towers.

Hollywood Burbank Airport's air traffic control tower was temporarily unstaffed Monday and flights were delayed or canceled due to staffing shortages amid the government shutdown.

Cracks in the air travel system are widening, as air traffic controllers bear the strain of an understaffed system and no pay until the government shutdown ends.