So, not to stir things up....BUT, leaving a store is easy. Let's say your kid who "never had a meltdown in public" has one on an airplane before you even leave the gate? Are you going to get off the plane and lose all the $$ you paid for your seats? Or do you just paste a smile on your face and do what you can to get through it?
Once again if you are actively trying to calm the child, then there is no issue. I have been next to kids who have screamed the whole flight but the parents were working their butts of trying to get things under control...way to go! Both my kids have ear issues, that we work very hard to control with medicine and trying to pop their ears, sometimes we are successful and other times they are in pain and cry. But the whole time I am working to get them to stop or trying different methods to reduce the pain they are in. We seem to have our FL flights down it is flying elsewhere that getting the timing of the meds to work.
I think a grocey store or a theme park is a much easier escape than an airplane. Even if you are offsite, unless you drove from Tampa and had no where to go, if things are not settling down, then a much needed break at the hotel should be part of the plan. People use the excuse of spending money to push everyone in their party from opening to close, even little kids. If everyone can handle that, then great, if they cant then you need to actively remedy the situation.
If you can not leave the park, then find somewhere cool and where the people are minimal, and deal with the tantrum/meltdown.
DH also was on a flight where two brothers, he thought about 6 and 7, were separated from mom by two rows, he offered to switch with the mom and take her aisle seat over his window seat. She said no thanks and the boys fought and were complete terrors on the flight. Mom never got out of her seat in fact he was pretty sure she took a nap. Now that was all kinds of rude.
We flew when DS13 was 2. He thought is was extremely funny to kick the seat in front of him, and with him in his carseat, his legs actually reached. Once I realized he would not stop, bc reasoning with a 2 year old does not always happen (See I Remember!). I held his leg the ENTIRE flight bc the minute I let go to pick something off the floor, he started kicking the seat. I kept apologizing to the man in front of us and he said he knew I was trying. So he would not get frustrated about me or DH holding his legs, we read book after book quietly to him, we had the Magnadoodle, food etc. When we landed the man and his family actually complimented how Dh and I handled the situation. Felt great as new parents! This was also the flight where USAir changed the seating arrangements and had the 2 year old sitting by himself and would not change it for us until we got to the gate. That whole flight was stressful.