MCALLEN – The extreme heat is causing flight delays for some Rio Grande Valley travelers between Las Vegas and McAllen.

Some travelers said they’re stranded in Las Vegas, waiting to board a flight back to McAllen.

Lizzy Hernandez and Cris Garcia’s trip didn’t end well. In fact, they said it hasn’t ended at all.

Their flight home, programmed for Wednesday, was delayed. They’re stuck in Las Vegas until Friday.

“We heard three different excuses: the generator, it was too hot and somebody called in sick and we had to wait for them to get here,” Hernandez said.

Allegiant Airlines said flights between Las Vegas and McAllen had to be delayed due to record-breaking temperatures. Temperatures in Las Vegas reached 117 degrees on Wednesday and 111 degrees in McAllen on Thursday.

The airline sent the following statement on their flight cancellations, which reads in part:

“Excessive heat warnings from the National Weather Service are currently in effect for Nevada and Hidalgo County, Texas. For the safety of our passenger and ground crew, the flights were rescheduled.”

Hernandez and Garcia said they boarded and de-boarded a plane two times on Wednesday. They added the temperatures inside the aircraft weren’t much better than outside.

“They kept clocking about 100 degrees or hotter. They ended up de-boarding us off the plane,” Garcia explained. “And that’s when I almost collapsed right outside the plane. I just remember waking up and I had EMTs; they were trying to check my pulse.”

Other Allegiant customers told CHANNEL 5 NEWS they went through similar experiences.

Victor Hernandez and his wife said they flew back to the Valley Wednesday morning after several delays.

“We were a little scared because there were people who vomited, and a lot of them changed to another airline because of the heat,” said the Hernandez’s.

Allegiant was the only airline delaying flight out of McAllen on Thursday.

McAllen airport officials said airlines make the call whether it’s safe for a plane to take off.

We’re told the heat can cause problems for aircrafts taking off. The air becomes much thinner, meaning the plane needs more speed and more runways to take off.