Commercial airlines make a substantial investment to ensure every plane is airworthy at every take-off. From the moment the aircraft door closes at departure to the time it's re-opened upon arrival, an airline can expect to spend $2,550 an hour, according to an International Civil Aviation Organization conference report. Operations and maintenance accounts for $590, or approximately one-quarter, of this hourly expense. Recertification is required whenever a plane undergoes repair, such as damage from a lightning strike or bird strike as well as on-ground scrapes and bruises. Researchers at the University of Virginia School of Engineering and the NASA Langley Research Center are working on ways to make re-certification simpler, more efficient and more cost-effective. Harold Haldren, who earned his Ph.D. in electrical engineering from UVA in 2020, developed a novel way to find weaknesses in the adhesives that hold together parts of aerospace vehicles. Haldren developed the method in collaboration with his advisorMool Gupta, Langley Distinguished Professor of electrical and computer engineering, and Daniel Perey, William Yost and Elliott Cramer, who lead research projects and programs for NASA Langley'sNondestructive Evaluation Sciences Branch. “Few people realize that most if not all airplanes flying must be bolted and riveted together. This is because the industry lacks an approved method to certify the structural integrity of a bonded joint,†Perey said. Perey explained that plane parts are fabricated with composite materials that work better when glued or bonded; drilling holes into the materials weakens the material. “This is the holy grail of the structural composite community—to verify the integrity of a bonded joint after it's been in service so that we can forego secondary bolting and riveting,†Perey said.