Charles J. Colgan, an aviator and businessman who became the longest-serving member of the Virginia Senate, where he was known for his advocacy of the development of Prince William County and for his steady-handed stewardship of state finances, died Jan. 3 at a hospice center in Aldie, Va. He was 90.

The cause was a vascular ailment, said a daughter, Mary C. Finnigan.

“Chuck was a champion in the Virginia Senate for the people of Prince William County and the entire Commonwealth,” Virginia Gov. Terry McAuliffe (D) said in a statement. “His passionate and bipartisan approach to getting things done should serve as an example for all of us as we continue the work he and so many undertook and passed forward to us.”

Mr. Colgan, a Democrat, was elected to the Virginia Senate in 1975 and represented fast-growing areas including Manassas and Manassas Park, in addition to parts of Prince William County. As the founder of Colgan Air, a regional commuter airline based in Manassas, he jokingly claimed the distinction of being the general assembly’s sole licensed airplane mechanic.

Until his retirement in 2015 at age 89, he held his seat throughout population shifts and redistricting, drawing the support of Republican voters as well as Democrats with his moderate and, at times, maverick voting record. In Richmond, where he served as Senate president pro tempore and in the influential role of budget conferee, he was widely known for his collegiality and pragmatism.

He “was really a landmark figure, not just in Prince William County, but in the entire commonwealth,” said Stephen J. Farnsworth, a political-science professor at the University of Mary Washington. “He’s a reminder of a more gentle and centrist era of Virginia politics, when Richmond was proud of the fact that it did not have Washington-style gridlock.”

“It never bothered us that we represented different parties, if we were working for the same goals,” said John C. Watkins of Powhatan, a Republican who also retired in 2015 after decades in the Virginia legislature. “That’s the way he saw fit to make it work.”

Mr. Colgan co-chaired the Senate Finance Committee and counted among his achievements the “sound financial management of Virginia,” Farnsworth said.

He took particular interest in the economic and educational development of Prince William County and the surrounding area. He was credited with bringing Northern Virginia Community College campuses to Manassas and Woodbridge as well as helping lead the establishment of George Mason University’s location in Manassas.

“He was one of the people who put George Mason on the map,” said Senate Minority Leader Richard L. Saslaw (D-Fairfax). “That whole community, Prince William County, is where it is today because of Chuck Colgan.”

Outside of education, Mr. Colgan devoted much of his legislative efforts to transportation, an issue of extreme concern to residents of his region who commute to and from Washington. He sought funding for the Virginia Railway Express and was credited with prevailing on state officials to widen a segment of I-66 west of Manassas, among other projects.

As a legislator, he was “low-key and soft-spoken, which may be one of the reasons he was so well-liked and successful,” said Larry J. Sabato, the director of the Center for Politics at the University of Virginia. “He wasn’t wont to call press conferences or get up on the soapbox. When he spoke, people really did listen.”

He was considered a reliable Democratic vote, but, as a Catholic, he opposed abortion rights and voted with Republicans on that issue. To avoid a government shutdown, he supported Republicans in a highly fraught budget debate in 2012, voting for an $85 billion budget package despite its exclusion of a $300 million appropriation for the expansion of Metrorail to Dulles Airport.

“We can’t just be concerned about Dulles,” he told The Washington Post at the time. “You can’t worry about this project and not the rest of the budget.” As for Democrats angered by his vote, he quipped, “They’ve been mad at me before.”

Charles Joseph Colgan was born in Frostburg, Md., on Sept. 25, 1926. When he was 5, his mother died of complications from a miscarriage. Shortly thereafter, his father died of pneumonia. Mr. Colgan spent the rest of his upbringing with his maternal grandparents on a farm in Grantsville, Md.

Mr. Colgan joined the Army Air Forces at the end of World War II, serving in Italy as an airplane mechanic. He later became a pilot and settled in Virginia.

In 1965, he joined other investors in founding a flight school and vendor of aircraft and fuel. The company, which he sold and reformed, grew into Colgan Air, a multimillion-dollar family business that provided commuter flights for airlines including Continental and US Airways. The outfit included dozens of planes by the time it was sold in 2007 to Pinnacle Airlines.

Mr. Colgan launched his political career when he joined the Prince William Board of County Supervisors in 1972, representing Gainesville. He served as board chairman before moving to the Virginia Senate.

A high school named in his honor opened in the Manassas area of Prince William County in 2016.

Mr. Colgan’s wife of 52 years, the former Agnes Footen, died in 2001.

Survivors include his wife of eight years, Carmen Alicia Bernal, of Gainesville; eight children from his first marriage, Charles J. Colgan Jr. of Nokesville, Va., Ruth C. Willis of Brewerton, N.Y., Michael J. Colgan and Dot Chaplin, both of Gainesville, Raymond T. Colgan, Mary C. Finnigan and Patrick S. Colgan, all of Manassas, and Timothy C. Colgan of Warrenton, Va.; a brother, Robert Colgan, of Manassas; 24 grandchildren; and 22 great-grandchildren.

Amid the 2012 budget standoff, Mr. Colgan called on his colleagues to restore the cooperative spirit that he had known as a new senator, and that many observers considered increasingly rare in an era of ever more divisive politics.

“Ladies and gentlemen, it is not like it used to be,” he said in remarks reported by the Washington Times. “Never . . . have I ever seen so much animosity or heard so much criticism.” He paraphrased the aphorism about politicians, who are concerned about the next election, and statesmen, who look ahead: “We should be concerned about the next generation,” he said.

An earlier version of this story incorrectly reported the location of a high school named in Mr. Colgan’s honor. Charles J. Colgan Sr. High School is located in the Manassas area of Prince William County, not in Gainesville, Va.

Jenna Portnoy and Laura Vozzella contributed to this report.