Britain’s airlines face significant disruption in a matter of weeks if the war in Iran continues throughout April, as a global jet fuel shortage has already forced carriers in Asia to slash service levels in a bid to manage supplies. Major UK-based carriers have said that they have between five and six weeks’ worth of supplies before their reserves will begin to run short as a result of the protracted closure of the vital Strait of Hormuz shipping lane. Several Asian airlines have already been forced to cancel some routes until as far…