I could tell by the grim tone of the caller that something bad had happened. My favorite airplane, a D-Day veteran DC-3 now hauling smoke jumpers, had just suffered some major damage and two friends had been at the controls. The crew had been taxiing for departure from Casper, Wyo.'s Runway 3 when the copilot noticed high hydraulic pressure on the landing gear system. For reasons unclear, the copilot, who was typed and had more than a decade of experience on this graceful lady, proceeded to retract the gear and before the startled captain could intervene, the left main began to fold. The aircraft quickly settled onto its left wing and all five propeller blades slammed on to the ground and bent. The PT-6 engine -- the airplane had undergone the Basler conversion -- was seriously damaged, along with critical components of the ribs, and the skin was wrinkled.

The aircraft, which we all adored, had survived anti-aircraft fire over Normandy but not the errant manipulations of a copilot whose mind took a little side trip during taxiing. The crew was returning the aircraft from a fire-fighting mission in the Southeast and was under pressure to get it back to its firebase to prepare for the Western fire season.

Adding to that pressure were the sniffles that the copilot had been experiencing that day. He had addressed that problem by ingesting two Benadryl Allergy capsules, a common over-the-counter (OTC) medication.

Since it was a non-prescription drug, there's an assumption that it can't be harmful. Wrong! This particular medication, also known as Diphenhydramine to pharmacists and medical doctors, commonly results in drowsiness, and has adverse effects on performance of complex cognitive and motor tasks, very necessary traits for a pilot operating an airplane.

In the Annals of Internal Medicine, the effect of a normal two-capsule dose of Diphenhydramine on simulated driving is noted to be worse than the effect of a 0.10 percent blood alcohol level. In other words, those two pills packed the equivalent punch of making a person legally drunk.

So let's say that you develop a case of the sniffles out on the road and you feel compelled to complete the flight despite being congested. During a quick visit to the grocery store or pharmacy you would find such products as Claritin, Clarinex, Zyrtec, Astelin and Allegra. While it might be tempting to believe that an OTC such as those antihistamines product won't impair a pilot's performance, that could be a dangerous self-delusion.

FAR 91.17 states: "No person may act or attempt to act as a crewmember of a civil aircraft . . . while using any drug that affects the person's faculties in any way contrary to safety. . . ."

However, antihistamines have been among the most commonly involved medications contributing to serious aviation accidents. Those drugs were cited as contributing factors in 78 fatal accidents in the last ten years in Part 91 and Part 135 operations.

The FAA does not publish a list of "approved" antihistamines and decongestants. However, according to Dr. Quay Snyder, a recently retired U.S. Air Force flight surgeon who has flown more than 48 types of aircraft ranging from gliders to the F-16 and who is now president of Virtual Flight Surgeons (www.aviationmedicine.com), only the "non-drowsy" or "daytime" products should be used. Incidentally, the only OTC non-sedating antihistamine authorized by the Federal Air Surgeon for use during flight duties is Claritin.

Be especially careful to watch out for products which may contain sedatives. Products such as Unisom and multi-symptom cold relievers such as Alka-Seltzer Plus Night-Time Cold Medicine and Vicks Nyquil Multi-Symptom Cold/Flu Relief use a sedating compound known as Doxylamine. According to the Physician's Desk Reference , known simply as the PDR, Doxylamine is one of the most sedating of the antihistamines and, thus, should be avoided while on flight duties.