An Allegiant Airbus A319-100, registration N318NV performing flight G4-33 from Las Vegas,NV to Bozeman,MT (USA), was enroute about 20 minutes into the flight, when a flight attendant noticed a strong, thick foul locker room smell near seat rows 7-12 and began to feel burning sensations in chest, eyes and nose. Other flight attendants confirmed smelling some odour, however, did not report to be affected. Headache, dizziness and shortness of breath followed. The flight attendant walked to the back of the cabin worrying she might faint, at the back of the cabin her fingers and arms cramped, she lost feel of her legs, and needed to be laid onto the floor, a collegue administered oxygen. Medical personnel on board was called out, three passengers came to provide first aid, however, because of the cramps had trouble to remove the clothing and connect a defibrillator with the medics suspecting she was tachycardiac. While the flight crew accelerated approach and landing to Bozeman, the passengers prepared for a landing with the flight attendant on the floor, with 3 of them holding her on the floor throughout the landing. The aircraft landed without further incident about 75 minutes after departure from Las Vegas, emergency services came on board, cut open the flight attendant’s clothes, connected an automatic external defibrillator (AED), diagnosed acute supraventricular tachycardia, used a wheelchair to get the flight attendant off the aircraft, then put her onto a stretcher and took her to the hospital.

According to information The Aviation Herald received from multiple sources the flight attendant had suffered two other fume events in 2019. The hospital confirmed the flight attendant was suffering from supraventricular tachycardia and determined the flight attendant had elevated levels of carbonmonoxide in her body and had been hyperventilating.

The aircraft remained on the ground in Bozeman for about one hour, positioned from Bozeman back to Las Vegas as flight G4-9206 and has not flown since landing back in Las Vegas. The aircraft is still on the ground in Las Vegas about 58 hours after landing in Bozeman.

https://flightaware.com/live/flight/AAY33/history/20211214/0244Z/KLAS/KBZN