BOULDER, Colo. -- Hitting at a 90-degree angle, the pilots of two planes that slammed into each other above Boulder Saturday had no warning, according to federal investigators.

"There was absolutely no communication between either of the aircraft collided and they were not in communication with air traffic control," said Jennifer Rodi, NTSB Investigator In Charge.

Three people died when a Piper Pawnee and a Cirrus SR 20 hit around one o'clock Saturday, killing 58-year-old Bob Matthews and his brother Mark Matthews, 56, as well as Alex Gilmer, 25.

Gilmer was towing a glider with pilot Reuben Bakker, a woman and her 11-year-old son on board.

Rodi said Bakker released the tow line just as impact was occurring and managed to guide the glider directly through a fireball before landing safely.

All three survivors have told the NTSB similar accounts, Rodi said, of virtually no warning before the crash on a crystal, clear blue sky day.

"And there are absolutely no maneuvers and no movement of the Piper Pawnee prior to the impact," Rodi said.

The area some three miles north of Boulder Municipal airport is uncontrolled airspace, meaning pilots don't have to get clearance from a control tower employee, Rodi said.

The manager of the airport couldn't recall any other similar crashes there since May of 1991.

"Mid airs are very rare. So that’s obviously the first double-take that you do," Tim Head, airport manager said.

Another pilot, Tracey Spence, told TheDenverChannel that he was in that air, doing "touch and gos" with a student pilot when he heard Bakker give a may day call.

Spence, though, said he heard nothing before the crash at roughly 8,300 feet.

"We both mentioned that today was kind of a day for pause, you know," Head said, gazing out his office window as light snow fell Monday. "To kind of remember that we need to be as safe as we can and that these incidences can happen. So having the snow fall kind of made everyone stop and reflect. You do lose people sometimes."

The pilots were flying by VFR -- Visual Flight Rules -- and had no requirement to communicate with anyone Saturday, both free to change direction as needed, Rodi said.

She also stressed that pilots are expected to use two-way radios to announce positions when in the air.

All of the wreckage has been taken to a hangar in Greeley where investigators will try to piece together what happened.

The final crash conclusions might not be available for six to eight months.