CNN) -- Two airplanes came too close to one another while attempting to land at a Detroit airport, a federal official said early Saturday, days after another close incident involving three jets at a Washington, D.C. airport.

A Delta flight from Phoenix was coming in to land Friday night at the Detroit Metro Airport as a small regional jet was trying to land, said Elizabeth Cory, a spokeswoman for the Federal Aviation Administration.

The two planes were separated by approximately two horizontal miles. Standard separation distance is three miles, Cory said, noting that an investigation is under way.

CNN first learned of the incident from an alleged passenger who said he could see a regional jet below them from his cabin window.

"Air traffic control was aware that they had a situation where separation was less than they would like," Cory said.

Both pilots had visual contact with each other and neither plane was at risk of colliding with the other, she added.

Friday's incident in Detroit comes a day after federal authorities acknowledged that three U.S. Airways-operated jets at Reagan National Airport came closer than they should have because of an air traffic control "miscommunication."

Feds investigate 3 planes flying too close at DC-area airport

The incident occurred Tuesday afternoon when air traffic controllers were making adjustments for landing and departing aircraft because of bad weather.

The Chautauqua Airlines flight came within 800 vertical feet and .82 nautical miles after takeoff of an arriving aircraft, identified as a Republic Airlines flight, authorities said.

The third plane involved was another Republic Airlines flight, which was taking off and came within 2.07 nautical miles and 800 vertical feet of the arriving flight.

"During the switchover of operations, miscommunication between the Tracon and the DCA tower led to a loss of the required separation between two regional jets departing from Runway 1 and a regional jet inbound for Runway 19," the Federal Aviation Administration said.

"Tracon," or terminal radar approach control, is a reference to a regional radar facility. "DCA" is the International Air Transport Association code for Reagan National Airport.

"At no point were the three aircraft on a head-to-head course," said Transportation Secretary Ray LaHood.

The FAA is investigating and plans to take "appropriate action to address the miscommunication" of Tuesday's incident.

"Such near misses and any operational errors are calls to action," Rep. John L. Mica, R-Florida, said after the Tuesday incident. "I'm asking our Aviation Subcommittee staff and FAA to thoroughly review what happened."

Last year, an air traffic controller was suspended for failing to respond to two planes heading into National Airport after he fell asleep on the midnight shift.

The two planes landed without incident.

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