Newark Liberty International Airport has had a very tough month. Many flights have been delayed or canceled because of problems with the airport’s communication and radar systems. Air traffic controllers, the people who guide planes safely in the sky, say these issues started because of a plan made during former President Donald Trump’s time in office.

In the last few weeks, there have been several times when air traffic controllers lost contact with planes. The worst incident happened on April 28, when the system completely stopped working for about 90 seconds. During that time, the radar screens went black, and controllers couldn’t talk to pilots for nearly a minute. Even though it was a short time, it could have been very dangerous. Since then, there have been three more outages, including one on Monday, even after the government tried to fix the problem.

The main issue is that air traffic control for Newark was moved to a facility in Philadelphia last July. Now, controllers in Philadelphia—more than 100 miles away—have to rely on phone and internet lines to get information about Newark’s airspace. If those lines fail, they can’t see the planes or talk to the pilots properly.

President Trump and Transportation Secretary Sean Duffy have said the Biden administration is to blame for these problems. They say the move to Philadelphia happened under President Joe Biden, so it’s his fault. But CNN found internal FAA documents that show the plan was actually started during Trump’s first term. The engineering plan for the move was finished just one month before the 2020 election.

Duffy has defended the plan but says the Biden administration “bungled this move” by not making sure the communication lines were strong enough. “Without addressing the underlying infrastructure, they added more risk to the system,” Duffy said at a news conference earlier this month.

Air traffic controllers say this was a bad idea from the beginning. They warned that moving control to another city could cause problems, and now those warnings seem to be coming true. One controller said, “It was a terrible idea,” explaining that relying on faraway systems makes it harder to keep flights safe.

Passengers at Newark Airport have faced long delays and cancellations because of these outages. Many travelers have been frustrated, not knowing if their flights will take off on time or at all. The government says they are working to fix the issues, but controllers worry that unless the system is changed, the problems will keep happening.

The FAA, which manages air traffic control in the US, has not yet given a full explanation for why these outages keep occurring. Some experts say the system needs better backup plans in case the communication lines fail again. Others believe the whole plan to move control to Philadelphia should be reconsidered.

For now, passengers flying through Newark will have to hope that the systems stay online. But with no clear solution in sight, the future of air traffic control at one of America’s busiest airports remains uncertain.