Dunkirk, N.Y. -- A man was proposing to his girlfriend when officials believe their plane crashed into Lake Erie Friday night.

The 24-year-old Pennsylvania man wanted to propose while flying over the lake and Niagara Falls, so he took her up in a small plane, NewsChannel5 reported.

The single-engine Cherokee was on its way back to Pennsylvania after a tour of the falls. The last known communication was made before 9 p.m.

Officials said they found debris and an oil slick in Lake Erie. Three plane seats and a seat cushion were also found three miles south of Port Colbourne, Canada.

On Sunday, the Buffalo Coast Guard conducted a massive search near Dunkirk, N.Y., which is about three hours from Cleveland.

"We're trying to keep a positive outlook on everything is what we're trying to do, hoping that they possibly made it to the shoreline and maybe got out of the aircraft. We just don't know," said family friend Andy Chalot.

The pilot, James Regal, 22, along with his passengers, Kevin Jesteadt, 24, and Lindsay Myers, 23, have not been found.