Tumbling and twisting through the air at speeds of more than 120 miles per hour, skydivers link up to create formations, dive head-first and land with pinpoint accuracy on quarter-sized targets.

Professional skydiving is a sport pursued by athletes year-round, but the season is beginning in the Midwest. For Chicago’s reigning national title champions, this season means rigorous training if they want to repeat their victory from last year.

At Start Skydiving, 1711 Run Way in Middletown, Ohio, 153 tandem jumps, where a student skydiver is connected via a harness to a tandem instructor, were booked for April 30, according to Start Skydiving employee Randy Mewson. The same is true for skydiving schools in Michigan and Illinois.

“We just started jumping [on April 29],” said Mandi Davies, employee at Skydive Michigan, 840 Grand St. in Allegan, Mich. “We’ve tried to jump the last few weekends, but the weather hasn’t been cooperating with us.”

According to Davies, the temperature is approximately 30 degrees colder at altitude, which is 10,000 feet. Professional skydivers cannot jump in bad weather, which includes sleet, rain, snow and

high winds.

“Our business months are July, August and September,” Davies said. “People like to come out when it’s a lot warmer.  And when we have a nice day, the phone rings quite a bit.”

Skydive Chicago’s season began on March 18 this year. However, the weather must be temperate for jumpers to take to the sky, and the Midwest season ends in the fall.

“The weather is gorgeous,” said Matt Stuart, skydiver and director of marketing for Skydive Chicago, 3215 E. 1969th Road., in Ottawa, Ill. “We just sent up our third airplane load. The weather just needs to cooperate.”

May through August are the busiest months for Skydive Chicago. On a good day, Stuart said there can be up to 200 tandem jumps booked.  Last year, Skydive Chicago had 7,500 first time tandem jumps and more than 60,000 sky dives.

“It’s just like snowboarding,” Stuart said.

“If you wear the proper gear, you’re good, but I like to skydive in shorts and a T-shirt. Skydiving is much more enjoyable when it’s nice out, but we will jump in the cold.”

The team from Skydive Chicago is currently ranked No. 1 in the U.S. and the facility is the largest drop zone in the world with 220 acres.

The International Aeronautical Federation World Air Games, which are held for one week every two years and include 10 air sports, are taking place this year. The team that wins first place at the 2011 U.S. Parachuting Association National Skydiving Championships of Canopy Piloting, which takes place from Sept. 14—17 in Texas, will represent the U.S. in the

Federation Aeronautique Internationale World Air Games.

“All your worries stay on the ground,” Stuart said. “You trust people that you’ve never met before with your life, and there’s a bond that you can’t explain.”

The Chicago team has a strong reputation. They won the national title last year. While the sport is popular in Chicago, there are larger communities of flyers in warmer climates where they can practice all year.

Doug Park said he knew he wanted to become a competitive skydiver after his first jump.

Park is the sponsorship and marketing director for Sky Systems USA Inc., 1407 Flightline Blvd., in Deland, Fla., a company that manufactures skydiving equipment,

“When I first started skydiving I loved it, but I thought there’s got to be more than just jumping out of an airplane and going ‘Yay!’” Park said. “It takes time and dedication, but I’m a competitive person. My whole life has been very competitive.”

Park has approximately 23,000 skydives, six world cups and several world championships. Now, he coaches and trains members of the U.S. Army how to skydive.

“I was looking for a greater challenge,” Park said. “I was looking for a purpose.”

Park is not alone. There are more than 40,000 active U.S Parachute Associate members. The sport includes several disciplines including formation skydiving, freeflying, canopy formation, wingsuit flying, skysurfing, freestyle and freefall.

According to the USPA website, freeflying is similar to aerial acrobatics. Jumpers fly in all directions, including over and around one another. Vertical formation is a type of freeflying that involves building a series of formations in a mix of upright and head-down orientations. Formation skydiving can range from formations of two to 400 people, which is the world record.

“On your belly you’re doing about 120 miles per hour,” Stuart said. “When you fly vertically, the average speed is 150 to 180 [mph], depending on how big you are and how many people are holding onto you.”

A second discipline of skydiving is known as canopy formation, in which jumpers open their parachutes immediately after leaving the airplane. They fly their parachutes together and create formations by holding onto one another’s canopies.

One of skydiving’s newest disciplines is wingsuit flying, This requires an aerodynamic jumpsuit, which allows a person to cover expansive horizontal distances while maintaining a slow descending speed.

Another high-performance equipment based discipline is canopy piloting. Skydivers use canopies to generate high speeds. Flyers can cruise several inches above the ground for extended distances at speeds close to 75 mph.

Skysurfing involves attaching a board similar to a snowboard or wakeboard but made specifically for skydiving.  A flyer performs aerial acrobatics in freefall, which include flips and spins.

Freefall style and accuracy landing are skydiving’s oldest disciplines. In freefall style, a jumper performs a set series of maneuvers in freefall as quickly as possible. For accuracy, a skydiver tries to land on a quarter-sized dot at the center of a landing target.

“There are so many levels of the spot,” said Laticia Freedman, flyer and office manager at Sky Systems USA Inc. “The reason why I love it so much from the instructional side is … it’s the look of success and accomplishment that students gain. It’s just an incredible thing.”

To try a tandem skydive, check out SkydiveChicago.com. The facility is located at 3215 E. 1969th Road., Ottawa, Ill., and is open now until the fall.