Was on a flight last week in IAH (737-900) and the air conditioning was non-functional. It was about 90-something degrees outside, and the inside of the aircraft was probably around that temperature, parked at the gate during boarding. Pilot announced the issue but that it should resolve once we depart. Pushed back from gate, engines started, temperature on the aircraft remained VERY hot. Pilot announced it should cool down upon takeoff. People are fanning themselves with safety cards and the the experience is very unpleasant, but tolerable for a short time.

Get to runway, pilot announces an issue with weather radar, we pull off to side and they contact maintenance. Meanwhile, it is VERY hot on the plane, getting hotter, and the pilot announces they need to contact maintenance to see what to do (about the radar issue, not the air conditioning). Passengers are very upset, many gasps after the announcement, and some passengers are clearly now in distress. Everyone is dripping in sweat, and it's starting to get pretty rancid.

A few minutes later they announce we will return to the gate and determine whether they will let passengers deplane as maintenance works on the radar issue. Get to gate, they don't want to let passengers off. I confront the FA and after she asks me to be patient that they are evaluating what to do, I state "respectfully, this is not a negotiation, I and many others on the aircraft are demanding to be let off the plane immediately". Passengers who overhear start applauding. FA goes directly to pilot who allows passengers to deplane (most/all do).

Here is my question and issue: there was weather in IAH that day. What if there were a ground stop and/or no available gates to go back to? We would be trapped in a very hot, unsafe environment. I was seated in the emergency exit row, and my fellow passengers and I were discussing when it would be acceptable to pull the red handle and evacuate the aircraft. I considered this a serious safety issue that could have ended much worse. What is someone had a heat stroke? Panic attack? Are passengers in that situation allowed to self determine evacuating the aircraft when the crew was unable to resolve the issue?

I contacted UA Customer Service and asked that they confirm this aircraft be taken out of service until properly repaired and to please report the safety issue and confirm resolution and policy around this. As you can imagine, I received 5000 miles and an apology, with no confirmation or clarification around air conditioning maintenance policy (FWIW, I don't want the miles, I want this to never happen again to me or any fellow travelers - this aircraft should never have been allowed to board passengers let alone depart the gate.)

Thoughts on next steps? Are there rules around this sort of thing?