I was recently reading Black Light, the very enjoyable sequel to Shooter, but I noticed in this book a plot hole that I have often noticed through the years. The scenario usually goes something like this: the bad guy flew his/her privately own aircraft for some reason, and the hero needs to know about the flight or plane. Inevitably the hero's sidekick says "He had to file a flight plan, lets check that." The only problem is that in most situations; no the bad guy didn't have to file a flight plan. It may have been have been almost 10 years since I obtained my private pilots license, but I was certain that I remembered that VFR (Visual Flight Rules) flights didn't require flight plans, while IFR (Instrument Flight Rules) did. Well I went to the FAA's website and found an online copy of the Aeronautical Information Manual, a rule book for pilots, and it turns I was still correct. Except for certain situations (chapter 5 section 1-6) VFR does not require the filing of a flight plan, although it is highly recommended to file a flight plan as a safety measure.
So there you go, if you're writing something; and the bad guy is flying his plane and you want the protagonist to find some information on the flight take an extra sentence to explain the situation of the flight that required a flight plan to be filed.