[SIZE=4]Hundreds of Boeing 737 and 777 aircraft worldwide may be flying with unsafe systems five years after a US airline regulators warned that they could pose a crash threat. The problem affects 737s built before the Max range that are currently grounded following two fatal crashes. They include the popular Boeing 737-800 range as well as the 600, 700 and 900 aircraft[/SIZE][SIZE=7].[/SIZE]