When two planes collided over Kearns three years ago, Utahns wondered how they could smash into each other on a relatively clear day.

Several days of testimony in federal court make it clear how two planes closing on each other at 300 miles an hour can go from a mere speck in the sky several seconds before a collision to a menace that fills the windshield in the fraction of a second before impact.Attorneys for the federal government believe the four pilots in the SkyWest metroliner and private Mooney had time to see each other and avoid the Jan. 15, 1987, collision that killed 10 people.

Attorneys for the families of the pilots killed in the Mooney believe the pilots did not and the air traffic controller at the Salt Lake International Airport should have alerted the SkyWest plane of the Mooney's presence.

Both sides finished closing arguments Tuesday. U.S. District Judge Thomas Greene gave attorneys until Nov. 19 to file any post-trial memoranda.

The attorney for the family of Paul Lietz - a pilot in the Mooney - argued the family lost between $484,000 and $725,000 in financial support due to Lietz's death.

The family of Chester Baker - owner of the Mooney - lost between $630,000 and $860,000 in financial support due to Baker's death, their attorney said. The government's assessment of economic loss is lower. The families also seek punitive damages.

The federal government settled with the families of the SkyWest pilots halfway through the trial.

Attorneys for both families argue that the air traffic controllers at Salt Lake International Airport had an obligation to issue a traffic advisory on the Mooney.

"They had the last and best opportunity to avert this collision and they didn't," said Ed Havas, attorney for the Lietz family.

The air traffic controller handbook requires controllers to issue traffic advisories - make mention of a plane's presence to nearby planes - on all planes "operating" in the restricted air space around the airport.

The families' attorneys argue "operating" means a plane in the air space. The government argued that "operating" means a plane has obeyed federal regulations by notifying the controller of its presence in the restricted air space.

The Mooney did not do that, the government argued. So it was not "operating" in the restricted air space, hence the controller was not required to issue a traffic advisory on its presence.

The government argued the accident happened because the Mooney violated federal regulations by straying into restricted air space and its pilots failed to maintain proper lookout for other planes.

"They were careless and reckless," said government attorney Bill Gallo. "They either knew - and I think they knew - or should have known they were in restricted air space."

Attorneys for the family claim the Mooney's altimeter - crushed in the collision at the 5800-foot mark - malfunctioned, showing an altitude 1,200 feet lower than the actual altitude. The planes collided at 7,000 feet above sea level. If the altimeter malfunctioned, the pilots may not have notified controllers of their presence in the restricted air space because they thought they were flying below it, the families' attorneys said.

The attorneys point to radar retrack, which showed the radar clearly picked up the Mooney as early as 10 minutes before the collision. The Mooney was seen by other controllers, they argued. Audio replay shows one controller did give a traffic advisory on the Mooney to another plane 10 minutes before the collision. Controller Mike Dawson, the controller in charge of the SkyWest plane at the time of the collision, was negligent for not seeing the Mooney on his scope, the families' attorneys argued.

Government attorneys claimed a radar glitch may have kept the Mooney off the controllers' scopes even though it showed up on radar playback. They believe the pilots - not the controller - had the primary responsibility to see other planes and avoid them.

"It boils down to the simple concept that you have to look out the window at where you are going. There's nothing magic about that. You have to look at where you are going. If you don't, you are negligent," Gallo said.