"We all are affected by cabin pressure and oxygen fluctuations, human, canine and feline, etc., but the fact that the Attendants were responsive and attentive to the situation may have saved Darcy's life", owner Michele Burt wrote in a thank-you letter to JetBlue, which was posted on Facebook.
The owners snapped a photo of Renaud posing, smiling, with Darcy before getting off the flight.
When Darcy began showing signs of distress on a JetBlue flight, crew members offered her oxygen through a small mask.
Michele Burt pulled her out from under the seat and put Darcy on her lap to try to help her relax.
When holding her and giving her water didn't help, two flight attendants provided an oxygen mask for Darcy to help her breathe, which may have saved her life.
Burt noted in her letter to the airline that she was traveling with her husband and three small dogs - including Darcy - and had done so for 12 years without any previous problems.
"I placed the mask over her face, and within a few minutes she became alert and after a short time she didn't want the mask", Michele said. Her tongue began to turn blue and she was having difficulty breathing.
The attendants brought bags of ice to try and cool the dog down, but Darcy wouldn't stop panting and continued to struggle.
When that didn't work, Spencer - who has a French bulldog of his own, Penelope - suggested an oxygen mask.
They brought Darcy water and ice but, as we found out from an interview Spencer on USA broadcaster ABC, the poor pooch needed more help. "I believe [crew members Renaud Spencer and Diane Asher] saved a life", said Burt.
Darcy has since recovered, and Burt says she won't fly with her again without her vet's OK. So I called the captain, and I told him, 'I think I need to use some oxygen, ' and he said, 'Go ahead'.
JetBlue said in a statement to ABC News its crew "want to make sure everyone has a safe and comfortable fight, including those with four legs".