A Las Vegas air traffic controller was on paid leave this week after mistakenly allowing one airliner to take off from a McCarran International Airport runway as another jet taxied across the same runway.

A federal official called the incident, which occurred one week ago today, a "runway incursion," but McCarran's director deemed it a "near miss."

No one was hurt and it did not appear the pilots of either plane had to take evasive action to avoid a collision between America West Flight 539 to Cleveland and Air Canada Flight 593 from Toronto just after 11 p.m. on Sept. 22, according to the Federal Aviation Administration.

"This should not have happened," Don Walker, an aviation administration spokesman, said Wednesday. "At this point, it appears to be a case of simple human error."

The agency is expected to take several weeks to conclude its investigation into what appears to be the most serious of five "runway incursions" -- incidents in which jets came too close to other planes or objects -- this year at McCarran, one of the world's busiest airports.

"It's an isolated incident. It doesn't happen frequently, that's for sure," said Clark County Department of Aviation Director Randall Walker. "This particular type of incursion, a kind we classify a near-miss, happens so infrequently."

The county runs the airport, while the FAA staffs the control tower.

The FAA-employed controller, who Don Walker did not name but described as a veteran controller who has worked more than 10 years at McCarran, had cleared Flight 539 to take off on Runway 25R while instructing another America West jet, Flight 778, to taxi to the same runway and hold for further instructions.

That's when the pilot of Flight 778 radioed the tower and asked for additional time to attend to an unspecified matter in the cockpit.

"The controller canceled the takeoff clearance for America West 778, apparently meaning to cancel the takeoff clearance for America West 539," Don Walker said. "Apparently, the controller canceled the takeoff for the wrong aircraft.

"He got the two America West aircraft confused," Don Walker said.

Around the same time, the Air Canada flight landed on Runway 25L, an east-west runway along Sunset Road that's parallel to and just south of Runway 25R. As America West Flight 539 began its takeoff roll on 25R, the controller instructed the Air Canada flight to cross 25R, using Taxiway A6, on its way to the terminal.

America West Flight 539 became airborne about 4,150 feet from the Air Canada flight, well under the 5,000-foot buffer planes are supposed to maintain on the ground. The Air Canada flight had just crossed the runway by the time the America West flight passed the intersection 100 feet overhead.

"They did not pass right over the top," Don Walker said.

There is no mandated distance between planes on the ground and in the air. "These planes were too close, obviously," Don Walker said. Planes in the air must be at least 1,000 feet apart horizontally.

Federal officials did not know how many passengers or crew were on each plane. The America West flight was an Airbus A320 capable of carrying 150 passengers, while the Air Canada flight was an Airbus A319 with seating for 120 passengers, according to the airlines' Web sites.

The controller was removed from duty immediately after the incident, and has been "decertified" as a controller, Don Walker said. The controller could be eligible for recertification if he undergoes additional training or takes similar remedial actions.

This year's four previous incursions at McCarran all happened since March 13 and each was deemed minor, meaning no significant action was needed to avoid a collision. Of those, two were blamed on controller error, one on pilot error and one on driver or pedestrian error, according to Don Walker.

There were no incidents from Oct. 1, 2004 -- the start of the FAA's current fiscal year -- and March 13, Don Walker said.

In the past year, McCarran had roughly 1.3 incursions per 200,000 takeoffs and landings. "That's typically what we see at a major airport," Don Walker said, adding the national rate is roughly one incursion for every 200,000 takeoffs and landings.

An incursion can be anything from a plane-to-plane collision to a jet barely failing to maintain a mandated buffer zone.

Don Walker said it did not appear the latest incident was due to overburdened controllers. The tower had its full compliment of five controllers on duty at the time, and the controller in question had been working for less than one hour.

"There's really no sort of overworked or understaffed issue that can be discussed here," he said.

The incident came as the nation's leading flight controllers' union has launched an ad blitz to highlight what it claims is a crisis in air traffic control staffing, resulting in a greater likelihood of dangerous incursions.

In recent months, the National Air Traffic Controllers Association has alleged that federal authorities have made drastic staff cutbacks while failing to adequately modernize and improve air traffic control infrastructure in recent years.

Federal officials have dismissed their claims.

Randall Walker said he believed flights at McCarran were safe.

Officials at the union and Air Canada did not respond to calls for comment Wednesday. A spokesman at America West deferred comment to the FAA.