Unlike the major U.S. airlines, Southwest Airlines viewed the car and bus as its chief competition. Advanced by Rollin King and Herb Kelleher, the company's founders, this notion permeated the company and drove its commitement to the most inexpensive fares and most frequent flights (up to 10 a day) between urban markets separated by 500 miles or less. This too flew in the face of prevalent industry practice, in which a “hub and spoke” system consolidated passengers from small markets at hub airports to assure relatively full planes for long-haul flights. It also meant that Southwest planes spent less time aloft relative to other carriers' planes. The time Southwest aircraft spent on the ground, as well as the physical stress on aircraft from a higher frequency of take-offs and landings, was costly and labor intensive: on the ground, a wide array of specialized handlers serviced the planes and processed the passengers.