A new app launched by a flight attendants union will allow crews and passengers to report planes that are too hot or too cold for comfort, part of a push for federal standards on aircraft cabin temperatures.

One of the biggest concerns during tarmac delays, particularly in the summer months, is when the cabin gets too hot while hundreds of passengers sit and stew as the plane sits on the ground.

Last summer, for example, a woman said her baby became overheated on a delayed flight stuck on the tarmac Denver. The baby was treated at a children's hospital, according to media reports.

The Aircraft Temperature Reporting App, called 2HOT2COLD, is being launched by the Association of Flight Attendants, which is also sending keychain thermometers to all of its members.

The union represents flight attendants at United, Spirit, Alaska, Frontier, Endeavor Air and other carriers. Delta Air Lines flight attendants are not unionized.

The Association of Flight Attendants, which in July filed a petition to the U.S. Department of Transportation asking it to set rules to limit extreme temperatures on flights, hopes to collect data through the mobile app to document the problem.

However, many travelers don’t carry thermometers with them and the app does not require verification of a temperature reading. Nelson said the union will be able to check the data with the airport or airline and reports from crews.

The flight attendants union says excessive heat can cause health problems like fatigue, dizziness, heat exhaustion or heat stroke.

Some airlines including Delta have their own policies on cabin temperatures, the union says.

“While some airlines... do try to address this issue, not all do,” said Association of Flight Attendants president Sara Nelson. “Because it’s not a regulation, often it gets prioritized last.”

Sometimes, airlines cut back on the use of auxiliary power units to save fuel and cut costs. Taking extra time to cool down a cabin can also cause delays, Nelson said.

She said setting a standard could help airlines coordinate with airports for mobile air conditioning units for planes on the ground or jetway air conditioning.

Nelson said in one case when cabin temperatures were in the “danger zone,” it turned out that aircraft had been relocated from a cold region to the Caribbean market, and heat was being pumped into the cabin.

The union is recommending target temperatures of 65 to 75 degrees, with a maximum allowed temperature of 80 degrees -- unless all in-flight entertainment units are in use, which can increase the temperature on the plane. In that case, the union is recommending a maximum allowed temperature of 85 degrees.