The Douglass A-26 Invader Air Tanker is powered by two 2,000 HP engines and empty, weighs about 23,000 Lbs. When it drops its 1200 gallons of fire retardant, it suddenly loses almost 11,000 Lbs. There should be no problem in getting the plane to climb after the drop. In fact, after a drop, keeping the plane from climbing too fast can be a problem.
When Pete begins his dive to put out the fire in Al's aircraft he first retards the throttles, the correct procedure to start a dive like that, but you hear the engine RPM increase at the same time. After entering the dive the engine RPM would increase due to aerodynamic effects on the propellers, but this would only begin after entering the dive not while still in level flight.
In the club, Dorinda, after changing into her new white dress says, "If you want to dance with this dress, you have to wash your hands." The firefighters wash and dry their hands and as they leave the bathroom, their shirts are still dirty, but when they are dancing with Dorinda, their shirts are clean.
When Dorinda rides her bike onto the airstrip to tell Pete that she loves him before he takes off, she jumps off her bicycle in front of the port engine and it isn't running. She climbs up on the plane to the cockpit scene but when she climbs down to her bicycle the engine is running and Pete is still on his feet in the cockpit so he couldn't have started the engine that fast. It was the reason she couldn't hear him saying "I love you".
When Pete is doing CPR on the school bus driver, at first he's sort of sideways to the bus. In a next shot, his back is to the bus and the bus driver is in a different position, too. In another shot, Pete is facing the bus and asking the kids what their names are, and then his back is to the bus again.
Pete's plane has the registry number N9425Z. Later in the film, the same number is visible on a different plane when Dorinda takes it out to aid the smoke jumpers; and before her splashdown, her plane now has registry number N4818E.
When Al Yackey is in the jeep, talking after inhaling helium, he's holding the balloon and driving with his right hand. The next scene shows Pete and Dorinda talking in front of the jeep and Al driving right-handed without the balloon.
At the climax of the film, a group of endangered smokejumpers is supposedly making their way to a river and safety. However, they are clearly moving uphill. You move uphill to get to a ridge (a fairly safe place to be in a wildfire); you move downhill to get to a river.
After a successful retardant drop, a tanker pilot lands at the tanker base and taxis to a stop. His plane is surrounded by cheering firefighters who appear to have been working on the fire as their fire clothes are dirty and they are holding firefighting tools. Real firefighters wouldn't be hanging around a tanker base after being out on the fireline, and if they were they would not be allowed to swarm a plane on the taxi way - too much chance of someone getting cut up by a propeller or run over by a plane.
After Ted Baker flies back to Colorado to get his tack card, he follows right behind the taxi car called "Follow Me" but it was unmanned and out of control and crashed into Derinda's house. Baker stops his Citabria right before the crash, when he instantly hops out of the plane the engine is already off and the propeller is stopped.