A United Airlines Boeing 777 lost a wheel during take-off in San Francisco on Thursday. The aircraft with around 250 people on board, which was supposed to fly to Japan, landed in Los Angeles a short time later without any problems. United stressed that passenger planes are designed to land with missing or damaged tyres. A Boeing 777 has six wheels on each side under the wings. Boeing is currently under intense scrutiny after a nearly new 737-9 MAX aircraft lost a part of its fuselage as it climbed after take-off at the beginning of January. The National Transportation Safety Board (NTSB) indi…