A change in the type of planes landing at the Renton Municipal Airport over the past 20 years might see them having to extend a safety area across Airport Way, through South Tobin Street and into the Renton High School baseball fields.

The possible expansion is due to more commuter jets landing at the airport in recent years and the need for larger safety areas to account for them.

“We’re seeing more activity from aircraft that have higher performance standards,” airport Manager Jonathan Wilson said, adding that Clayton Scott Field is now the fourth-busiest airport in the state, behind Sea-Tac, Boeing Field and Paine Field in Everett.

The city is currently working on a required Master Plan update for the airport and, according to Wilson, the larger planes coming into the airport these days might trigger Federal Aviation Administration rules requiring a huge new runway protection zone that must be kept empty for safety purposes.

Currently, the Master Plan is configured for the primary aircraft served in Renton to be a small turbo-prop plane that seats up to 12 passengers. It is what’s known as the airport’s “design aircraft” for planning purposes.

But since the last update, a new class of planes is on the upswing: small corporate jets.

“Really what we’re seeing is a lot more of the business-jet style using the airport,” Wilson said. “The numbers of corporate aircraft are up. And they’re way up.”

And with a larger “design aircraft” comes a larger protection zone than the airport currently has space for.

“Based on data we’ve seen, what we’re looking at now is that runway design code changing, possibly,”

The runway safety area is a space that surrounds the paved take-off and landing strip and is designed to give aircraft who leave the runway a structure- and population-free place to go.

Under the current designation, the runway safety area must be 150 feet. Because of the Renton airport’s unusually wide runway (due to its WWII-era construction for use by Boeing), the current safety zone fits entirely within the paved runway area.

But if the designation changes, the safety area jumps to 500 feet, and since extending a peninsula into Lake Washington is unlikely at best, that would mean the space would have to come from the south end of the airport, leading to a safety area that ends at Tobin and a protection zone that stretches almost to South Third Street.

FAA regulations specifically prohibit “residences and places of public assembly” in the RPZ.

“The question is how to deal with that,” Wilson said.

Marcie Palmer, outgoing City Councilwoman and Renton Airport Advisory Committee member, said she has been on the RAAC since 2001 and though this designation change has always been a possibility, the actual news of it was something of a shock.

“I thought oh … my … goodness,” Palmer said. “We’ve just seen a much quicker switch to the type of aircraft coming in than we expected.

“It snuck up on us,” she said.

So when the Master Plan update came up at a recent meeting, including word from the FAA that the city cannot deviate from the standards, “that was when I went ‘oh wow,’” she said.

Palmer said she realized then the scope of work that might be necessary.

“I think people are going to be stunned and overwhelmed with the thought,” she said, but added, “I don’t think we should panic.”

Wilson said the FAA has yet to formally accept the Renton analysis and may still keep the airport’s designation as-is; but even if the change is not made in this iteration of the Master Plan, Wilson said they will eventually have to deal with the issue.

“The door’s wide open on where we land with our runway design code,” Wilson said. “We’re not done yet.”

On a high note, any expansion of the airport would be eligible for 90 percent funding from the federal government, but that does not deal with the traffic on Airport Way or where the businesses, residences and high school playing fields would go.

But Palmer said this is all a product of the success of the airport, which is a good thing for the region and the city.

“We just happen to be in a good location,” she said. “We have to make what we have work best.”

Wilson said the city expects to hear from the FAA and, if necessary, begin a large public outreach on the issue beginning next year.

This story has been corrected: Due to a misunderstanding, Marcie Palmer’s starting date on the Renton Airport Advisory Committee was incorrect in the print edition of this story. Palmer has been a member of the RAAC since 2001. It has been corrected in this version.