Perimeter Rules (No, This Doesn’t Involve Math)

In this recent conversation on the Today in the Sky blog, I mentioned something about the perimeter rule at New York’s LaGuardia airport. I realize that a lot of people have probably never even heard of this thing, so I’ve decided to devote a post to it.

If an airport has a perimeter rule, it means that there is a certain distance from that airport beyond which flights are not allowed to go. Forgetting about the whole Wright Amendment thing in Dallas, there are two airports that have perimeter rules in the US: New York/LaGuardia and Washington/National. Before we get into the details, the first question many people ask is . . . why?

Washington had a brand new airport at Dulles and New York had one at Idlewild (later to be JFK). The problem was that nobody wanted to use them since both National and LaGuardia, the main airports at the time, were more convenient and preferred by customers. So, a perimeter rule was enacted to continue to allow short haul flights at the old airports but requiring longer haul and most international flights to use the new one.

Over the years, the perimeter rule became the political rule as politicians kept expanding it so their home airport would be included. That brings us to today. The perimeter rules look like this:

Maps generated by the
Great Circle Mapper – copyright © Karl L. Swartz.
National now has a 1,250 mile limit for all flights. That was not the original number, but it now conveniently includes Dallas/Ft Worth at 1,192 miles and Houston/Intercontinental at 1,208 miles. Of course, that wasn’t enough for everyone, so they started allowing exceptions.
The first round was for six roundtrip exemptions sponsored by John McCain, Senator from Arizona. Not surprisingly, his hometown airline America West won three of the six exemptions. A few years later, they added another six exemptions for a total of twelve. That’s where we are today. These are the exemptions:
  • United once daily to Denver
  • Frontier three times daily to Denver
  • Alaska twice daily to Seattle and once daily to Los Angeles
  • Delta once daily to Salt Lake City
  • America West (now US Airways) three times daily to Phoenix and once daily to Las Vegas
As for LaGuardia, the situation is a little different. They also saw their rule pushed further and further to allow points in Texas – Dallas/Ft Worth is 1389 miles and Houston/Intercontinental is 1,416 miles – but even more blatant is the exemption of all flights to Denver.
The most interesting point of this rule in New York is what I addressed in the original post above. The rule applies six days a week but not on Saturdays. Over the years, several airlines have tried to make the Saturday-only long haul flights work, but they haven’t really caught on that much. The following are the flights that operate only once each Saturday:
  • US Airways to Aruba
  • Continental to Aruba
  • American to Vail during the winter
  • Delta to Las Vegas, Los Angeles, and Salt Lake City

Now that JFK and Dulles have certainly come into their own, the perimeter rule has outlived its purpose. These days it’s just an unnecessary rule that artificially prevents airlines from meeting demand for long haul travel from close-in airports.

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