BALTIMORE (Map, News) - On-time accuracy for flights leaving and arriving at Baltimore/Washington International Thurgood Marshall Airport improved last month from the year before, according to federal data released this week.

BWI was the third-most on-time airport for arriving flights, with 85.97 percent of planes landing as scheduled, up from fourth place with 82.78 percent last year, according to data from the U.S. Department of Transportation’s Bureau of Transportation Statistics. For departing flights, BWI ranked eighth with 87.02 percent of planes taking off on time, up from 81.85 percent, 17th place, last year.

While BWI benefits from the increases in on-time performance, it’s not something the airport controls, BWI spokesman Jonathan Dean said.

“Flight delays are well beyond the control of individual airports,” he said. “[But] BWI is generally recognized as a low-delay airport in the Northeast.”

BWI and Boston’s Logan International Airport were the only two Northeastern airports in the top 10 in on-time departure performance, and BWI was the only one in the top 10 for on-time arrival performance.

Dean said the two major factors influencing the numbers were regional air traffic control congestion, controlled by the government, and the weather. A dry summer and a generally clear grid both helped the airport, he said.

“When bad weather hits, the airlines don’t have the ability to recover quickly,” he said.

“Weather was not much of an issue here,” he added. “The drought was bad for farmers and on our lawns, but perhaps beneficial to air travel.”

BWI’s largest carrier, Southwest, may also have helped its on-time numbers. The airline has introduced a system allowing planes to remain on standby and step in for newly arrived jets that need work and would otherwise cause departure delays, according to spokeswoman Brandy King.

The airline also includes primarily direct flights, avoiding delays that can result from “hub and spoke” systems used by other airlines that require changing flights at certain major airports, King said.

“BWI being one of our larger operations, that would be one of our focuses, making sure that airport runs smoothly,” she said. “When one aircraft gets behind, [it] has a tendency to trickle through the system.”

acahall@baltimoreexaminer.com