Delta Air Lines has learned that summer is a good time to prepare for winter � and how to de-ice planes so they can keep flying safely in freezing temperatures.

Every summer, Delta brings about 400 workers to Minneapolis to a three-day summer de-ice “boot camp.� They go through computer-based training, watch demonstrations by instructors, and then practice spraying down a plane � using water instead of the chemicals found in de-icing fluid.

The boot campers, who rotate through in groups of 10 or so, return to their home bases and train 6,000 co-workers before October, says Jeannine Ashworth, vice president of airport operations for the Atlanta-based airline.

Here’s how the de-icing process works: Big trucks with tanks of deicing mixture pull up alongside a plane, and an operator in a bucket at the top of a long boom sprays hot fluid that melts ice but doesn’t refreeze because of the chemicals it contains, mainly propylene glycol.

It takes anywhere from a few minutes to 40 minutes or longer to de-ice a plane, depending on the conditions and the size of the plane.

Planes need to be de-iced because if left untreated, ice forms on the body and wings, interfering with the flow of air that keeps the plane aloft. Even a light build-up can affect performance. In worst cases, ice can cause planes to go into an aerodynamic stall and fall from the sky.

De-icing “is the last line of defense in winter operations for a safe aircraft,� says Dustin Foreman, an instructor who normally works at the Atlanta airport. �If we don�t get them clean, airplanes can�t fly. They won�t stay in the air. Safety first, always.�

The hardest part of the training? Getting newbies comfortable with the big trucks, says Michael Ruby, an instructor from Detroit who has been de-icing planes since 1992, when he sprayed down Fokker F27 turboprops for a regional airline.

�The largest vehicle that they�ve ever driven is a Ford Focus. The trucks are 30 feet long, to say nothing about the boom going up in the air. There are a lot of different switches,” Ruby says. �The first time you�re driving something that big � the first time you�re going up in the air � it�s intimidating.�

Minneapolis is a logical place for learning about de-icing. Delta de-iced about 30,000 planes around its system last winter, and 13,000 of those were in Minneapolis.

The boot campers, however, come from all over Delta’s network � even places that are known more for beaches than blizzards.

�I would never have guessed that Jacksonville, Florida, or Pensacola or Tallahassee would need to de-ice aircraft � and they do, so we train employees there as well,� Ashworth says.

(AP)