Travellers booking flights are being warned that a 'critical threshold' is 'just weeks away' as airlines grapple with the crisis facing the industry. Airlines have scrapped more than 13,000 flights due to depart in May as a result of jet fuel shortages and soaring prices - with one analyst today branding the situation a looming 'disaster'. The Times reports that British airports have confirmed cancellations on a number of key routes, including four Brit travel spots: London Heathrow to Beijing,