A scissor hub occurs when an airline operates multiple flights to an airport that arrive at the same time, swap passengers, and then continue to their final destination.[29] Air India operates a similar scissor hub at London's Heathrow Airport, where passengers from Delhi, Ahmedabad, and Mumbai can continue onto a flight to Newark.[30] An international scissor hub could be used for third and fourth freedom flights or it could be used for fifth freedom flights, for which a precursor is a bilateral treaty between two country pairs.