An Allegiant Air flight heading to Pittsburgh was forced to return to St. Petersburg for an emergency landing.

The plane made an emergency landing Wednesday at the St. Pete-Clearwater International Airport due to pressurization problems. It was the second emergency landing at the airport this month.

The airline cancelled six flights at the airport Thursday, citing "operational needs."

Three of those flights were heading to Tennessee, upstate New York and Oklahoma. The other three were coming to St. Pete-Clearwater from those same locations.

We reached out to Allegiant air looking for answers and received the following statement.

"Allegiant is currently operating in our peak travel season, flying a very heavy schedule of flights each day. In addition to this high demand, we have a had a number of unforeseen and unusual events that have taken aircraft out of service.... We never want to delay or cancel a flight, but the safety of our passengers and crew is our number one priority."

Allegiant Air customer Jim Sweger waited 45 minutes, then another hour with customer service trying to rebook his flight to Pittsburg after the one he was on last night had to turn back around with cabin pressure issues.

“My luggage is in Pittsburg right now and the car rental all messed up," he said. "I have to go to the rental agency now and try to straighten that out.”

Now, through their union, Allegiant pilots are calling on the airline to invest in maintenance.

“Passengers shouldn’t have to wonder if their Allegiant flight will be the next one to make an emergency landing,” said union president Daniel C. Wells.

For some passengers any fixes may come too late.

A passenger who said her Allegiant flight was also cancelled last night is done with the airline.

"I'll never fly with them,” said Kathey Schroeder, passenger. “I'll just lose the $200 voucher. Or give it to somebody else who wants to jump on because I'm done."

Schroeder said she already returned her rental car is stuck here looking for a way to get to the airport in Tampa. She said her husband is booking her a flight there on a different airline.

Officials from the Nevada-based airline apologized for the disruption and said they'll offer affected passengers a $200 voucher for a future flight. Officials say they're also waiving change fees and fare differences for passengers who have to reschedule.