Under-inflated tyres caused a learjet to crash killing four people and ... The National Transportation Safety Board also said a design flaw in the Learjet 60 and a decision by the flight's captain to abort takeoff in Columbia, South Carolina, were also at fault in the accident. Investigators told the board they found that operators of air charters often are not aware how rapidly the tires of some business jets can lose pressure and are not checking tire pressure frequently enough. "This accident didn't have to happen," ... The board also said the Federal Aviation Administration and Learjet Inc., a...