As the government shutdown drags through a second week with no end in sight, staffing issues at airports across the United States are increasingly creating delays for travelers and could start to present a major security risk as air traffic controllers and safety inspectors remain off the job.

TSA officers, air traffic controllers, and pilots are warning the shutdown will cause long-term problems for air travel in the US. Some TSA officers have already quit rather than work without pay, and if the shutdown continues, union leaders expect more will start looking for new jobs, in addition to calling out sick.

Air traffic control and TSA have seen their national workforce shrink in recent years, and under the shutdown, training of new hires has been ruled unessential. Upgrading technology has also been put on hold, as has some safety inspections and oversight.

That means it will be harder for the federal aviation workforce to bounce back, even after the shutdown ends.

“The loss of officers, while we’re already shorthanded, will create a massive security risk for American travelers since we don’t have enough trainees in the pipeline or the ability to process new hires,” American Federation of Government Employees TSA council president Hydrick Thomas said in a statement Tuesday.

Transportation security officers “already do an amazing job without the proper staffing levels, but if this keeps up there are problems that will arise — least of which would be increased wait times for travelers,” Thomas added.

