Companies are learning first-hand about the challenges of building quiet supersonic jets. Both Florida Today and CNBC report that Aerion Supersonic is suddenly shutting down. The would-be maker of quiet supersonic business aircraft said it had trouble securing funding in the “current financial environment” and was going through the “appropriate steps” in light of the situation.

The company had focused its attention on the AS2, billed as the first privately-designed supersonic business jet. It was meant to cruise at speeds over 1,000MPH without the sonic booms and cabin noise that plagued aircraft like the Concorde. It was supposed to fly by 2024 and enter service by 2026. Aerion had a number of high-profile partners, including Boeing and GE, and garnered praise from Florida’s governor when it unveiled plans to build a factory at the Orlando Melbourne International Airport.

Aerion didn’t say what would happen to the company’s assets following the shutdown. The company had been touting new developments as recently as late April.

This isn’t the end to private supersonic air travel. Boom Supersonic is still developing its Overture airliner with hopes of passenger flights by 2029.

However, it’s also not a surprising outcome. Aircraft design is expensive by nature, and that’s particularly true for cutting-edge technology like this — Aerion said it would take $4 billion to develop AS2. And while the COVID-19 pandemic appears to be easing, air travel is far from a certain investment between public reluctance and companies that increasingly work from home. The audience for these jets just isn’t as large as it was a couple of years ago, and it might not be for a while to come.