The heads of American Airlines and US Airways are telling Illinois’ two U.S. senators they are still committed to a plan to modernize Chicago’s O’Hare International Airport.

American’s Tom Horton and US Airways’ Doug Parker wrote in a letter to the senators that they “have our commitment that we will continue to work collaboratively with the city and are supportive of cost-effective, demand-driven projects at the airport.”

Sens. Dick Durbin (D-Ill.) and Mark Kirk (R-Ill.) do not want a pending merger, which still needs to be approved by the U.S. Dept. of Justice, between the two airlines to affect the planned billion dollar airport expansion.

Durbin, in particular, said he met with Parker earlier today.  

“When we hear there’s change, that American may be merging with US Airways […] I wanted to sit down with [Parker] and make certain that his commitment to O’Hare and to Chicago was solid,” Durbin said in a phone interview Wednesday. “I wasn’t asking him for an iron-clad agreement about how they’re going to spend money if the merger is approved. I just wanted to make sure that he understood the importance of American to the scene at O’Hare.”

He added that Parker will be meeting with Chicago Mayor Rahm Emanuel, a supporter of the O’Hare expansion, about the project “in just a few days.”

An American Airlines spokeswoman declined to comment.

Durbin and Kirk sent a letter to the American heads in February, reminding the airline the O’Hare project “will create 195,000 more jobs and generate $18 billion in annual economic activity,” adding the merger faces “regulatory scrutiny” by legislators before being approved.

On Wednesday, Durbin said the letter was sent after he met with Emanuel in Washington.

“Mayor Emanuel made it clear to us that this merger was something we all ought to watch carefully and Sen. Kirk and I decided the best thing to do is to put it in writing, on the record. Let Mr. Parker and Mr. Horton know that we’re watching this merger and want to know the impact on Chicago,” he said.

Stephen Schlickman, the Executive Director of the Urban Transportation Center at the University of Illinois at Chicago, said the senators are especially worried about the status of O’Hare as a major worldwide transportation hub.

“When O’Hare coughs, the rest of the system gets a cold, so it has a major national and federal interest,” Schlickman said in a phone interview. “[Politicians] are going to give it a high priority and express their concerns to whomever they need to.”

The billion-dollar O’Hare Modernization Program hinges on agreement between United and American Airlines. In 2011, Transportation Secretary Ray LaHood helped broker the $1.17 billion deal between the federal government, the city and the airlines.

The project aims to bring additional runways to O’Hare and decrease delays at the airport.

American Airlines and US Airways Respond to Sens. Durbin and Kirk by