Consider yourself lucky with a four hour wait. Back in April of 2007, my party of five was enroute to KOA from BOS with a change of planes in ORD to flight 73. This was a 767-300. Once on the ground in ORD we were greeted with a little snow storm.

We boarded the plane on time but had to sit for 2 hours while waiting to get deiced. Around 11:00 a.m. we left the gate for our departure to HNL. Pilot turns the plane onto the runway, guns the engines, we start moving forward, then all of a sudden, we aborted take off, slowed to a crawl and head back to the terminal.

If I recall, after listening to the converstions of the flight crew, the problem was a secondary warning device, I believe for the engine had activated. Mechanics came on board but could not fix the problem. The plan was to be fly the plane to LAX, even with this issue. While this happened, AA would get another 767 there to transfer passengers, luggaage and cargo. This did not happen for a variety of reasons. Thats a different story.

Like someone said, there are various rules, regs, equipment, etc that would restrict a plane from flying over water. Even the problem you described could have happened once the plane landed in LAX not prior. Who knows. Just feel safe that AA got another plane for you that did not have problems.