Air New Zealand and Virgin Australia say ash billowing out of the Hunga Ha'apai volcano has forced them to cancel flights in and out of Tonga, stranding hundreds of people.Air New Zealand says about 300 people were booked yesterday and today to travel on two flights from Tonga to Auckland.Air New Zealand had to divert its Auckland to Tonga flight yesterday to Samoa, and cancelled the same service to the country today.Virgin Australia says it cancelled a Sydney to Tonga flight yesterday, and a Tonga to Auckland flight early this morning.The general manager of the Scenic Hotel in Nuku'alofa, Graeme Horsley, whose flights to Auckland was cancelled, says ash has only recently been blown across the country.\Over the last couple of days the weather pattern has changed and the wind is actually blowing the ash and smoke across the island.\New Zealand Civil Aviation Authority meteorologist Peter Lechner said the Hunga Ha'apai volcano was sending volcanic ash more than 9,000 metres in the air.\The plume is stretching up to about 30