The U.S. government shutdown, which is entering its second week, reportedly caused flight delays at several airports across the country for a second straight day on Tuesday, with the Federal Aviation Administration preparing for even more airport staffing shortages.

Air traffic controller shortages reportedly affected travelers at Boston’s Logan airport, Philadelphia International Airport, George Bush Intercontinental Airport in Houston, Nashville International Airport, Chicago O’Hare International Airport and Harry Reid International Airport in Las Vegas, according to the FAA.

The delays came after the air traffic control tower at the Hollywood-Burbank airport was not staffed for several hours on Monday.

Staff at San Diego’s Control tower stepped in to help.

“What will happen is an inconvenience to the traveler,” former FAA and NTSB safety investigator Jeff Guzzetti told NBC 7. “There’ll be more delays and cancellations, but in terms of safety, I think the system will remain safe.”

San Diego International Airport is not facing any staffing challenges.

“San Diego International Airport (SAN) continues to operate normally, and essential federal aviation personnel (including air traffic controllers, FAA operations, and related support staff) are anticipated to remain on duty,” sirport staff said in a statement sent Tuesday to NBC 7.

It remains unknown when the shutdown will end. On Monday, the U.S. Senate again failed to pass legislation that would reopen the government.