Boeing 247D

The Boeing 247 was the first modern airliner, which Boeing delivered to United Airlines in 1933. According to the Smithsonian Air and Space Museum, this airliner revolutionized by combining technological improvements such as retractable landing gear, two supercooled engines, and controllable pitch propellers, with passenger confrontations like a soundproofed cabin with air conditioning. The Boeing 247D had a top speed of 200 mph and a cruising speed of 187 mph. It could also hold ten passengers and three crew members.