Questions: I was flying into Las Vegas and we were landing east to west as other flights were taking off west to east (I could see the planes). Is this common?

-- submitted by reader Mike Wright, Oklahoma

I recently saw a 747 and 757 take off and land simultaneously at DTW, in opposite directions. I never noticed this in many years of observing planes there. The winds were calm and may have been shifting.

-- Jason Hill, Washington Twp, Mich.

Answer: It sounds like you both saw the changing of the runways at the airport. This occurs when the wind shifts, causing an airport to alter the runways in use for takeoff and landing. During this transition, it is possible to have landing aircraft using a runway that is opposite of the takeoff runway. You probably saw the last airplane landing on the old runway and the first one for the new runway. It is not normal, but it does happen occasionally.

Q: At MSP, the controller will pull you out of your landing approach if your speed is overtaking traffic on the parallel runway. What does your speed have to do with other landing traffic?

-- Bob Cradle, Bloomington, Minn.

A: If your airplane is overtaking another and separation will be lost, the controller is required to break out the overtaking aircraft unless the pilots can see the airplane visually. If the runways are sufficiently far apart, then this requirement is not necessary.

The conditions you describe at MSP would apply during conditions where the pilots of the overtaking airplane cannot see the other airplane and the runways are not spaced far enough apart for parallel landings. This is not unique to MSP.

Q: What is the minimum horizontal separation distance when landing two planes on two parallel runways? I was flying into Logan airport and another jet was landing at the same time on a parallel runway. It seemed like if we had to abort, the landing it would have put us in a dangerous position.

-- Evan, Boston

A: Pilots have to have visual contact to land simultaneously if the runways are less than 6,000 feet apart. While the runways in Boston are fairly close together, the ones in San Francisco are only 750 feet apart -- it is one of the closest parallel runway configurations in the U.S. If a go-around is necessary, the pilots fly divergent headings.


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