LÉOGÂNE, Haiti — On a good day, a stray cow might be the only obstacle to landing the small planes bringing oxygen, crutches, baby formula and other supplies that will be put to immediate use at a hospital set up in a nursing school dormitory here.

On a bad day, like one recent Sunday morning, the pilots circled overhead, waiting while a Humvee towed an abandoned truck off the landing strip with a hastily borrowed chain.

The landing strip, in fact, is actually a stretch of highway flanked by sugarcane and banana trees, currently the only way to fly into Léogâne, a city near the epicenter of the Jan. 12 earthquake. The flights, by volunteer pilots flying mostly at their own expense, are part of an unconventional relief mission to get supplies to some of Haiti’s most remote areas.

The planes have landed on a dirt airstrip in Jérémie, a 10-hour drive from the capital, Port-au-Prince, bearing the sole supply of X-ray film to an area deluged by earthquake victims with broken bones. They have spirited out the wounded and ferried in spaghetti and beans. The conditions vary from a paved runway and a control tower in Jacmel on the southern coast, to a gravel runway in Port-de-Paix in the north, where a man manages air traffic without the aid of radio or radar. The situation on the ground, where hungry Haitians sometimes crowd the tarmac, can be unpredictable.

On Sunday, two Americans, Ryan Courtemanche, 26, and his co-pilot, Bernard Antonovich, 22, kept their cool as they barreled down in a Cessna Grand Caravan whose wings were 20 feet wider than the two-lane road.

In preparation, United Nations troops had cordoned off the road, but the clearance was still so narrow that on an earlier flight, a wing clipped a tree, and rebar protruding from an unfinished wall had been bent back to clear the way. The runway is also shorter than normal, so the pilots braked hard.

“Welcome to Léogâne,” Mr. Courtemanche said genially, as if he were doing his usual job of shuttling the well-heeled to Nantucket and St. Barts.

The charter company he and Mr. Antonovich work for, Tradewind Aviation, based in Oxford, Conn., donated their time and the use of the Caravan for dozens of relief flights. “I never thought I’d be flying to Haiti,” Mr. Courtemanche said, “and I never thought I’d be flying on a road.”