Drug smugglers taking to the skies to ferry drugs across the border.

They're using ultralight aircrafts as the new tool to smuggle drugs and U.S. Border Patrol officials said the number of encounters are increasing.

U.S. Border Patrol officials from the El Centro sector said it's a sign that drug smugglers are becoming desperate since the border is becoming more secure.

Hang gliders which are usually used for recreational purposes are now being modified to carry drug loads.

Drug smugglers have dug tunnels, sailed boats, built ramps over the border fence and even tried to hide drugs inside of bricks to try and succeed in their smuggling runs.

But now, ultralight aircraft seem to be the new trend among Mexican organized crime groups, now that man power, technology and security has been stepped up along the Southwest border.

"These criminal organizations have become a little bit more desperate and they find dangerous means of transporting their narcotics thru the border via these ultra light aircraft," Victor Lara, Border Patrol spokes for the El Centro sector said.

Lara said they had 118 incursions during the 2009 fiscal year.

The number of incursions doubled last year and they had more than 70 encounters in the first four months of this year.

Lara said the modified hang gliders can zip across the border within minutes.

So now agents have to turn off their engines and roll down their windows.

"They're detected by means of hearing them because they fly at low levels," Lara said. "So the only way of detecting these guys is by hearing these guys at night."

Ultralights make a sound a little louder than a lawnmower.

He said these light-weight planes have a single engine and carry one or two people.

Lara said smugglers won't carry drug loads by the ton as they once did. Ultralight carry only a few pounds at a time.

"It doesn't take a lot of skill to fly these so that's why they pose a major threat to everybody," Lara said.

He said agents can't shoot down the ultralights because it would place the public at risk and they could also crash into power lines.

Agents can only follow the planes to their destination.

They also tip off the Mexican authorities in case they fly back across the southern border.