Passengers on multiple United Airlines flights say they were stranded aboard planes for hours at Newark Liberty International Airport on Wednesday, with some flights eventually canceled after lengthy delays on the tarmac. Alan Tuerkheimer said he boarded his flight home to Chicago at 5:40 p.m., but what followed turned into a seemingly never-ending nightmare. “We boarded the plane at 5:40 p.m. — that’s when all the chaos and problems ensued. We ended up sitting on the tarmac for seven hours,” Tu