United Airlines CEO Scott Kirby has warned that the airline may raise summer fares by up to 20% to offset the rising cost of jet fuel. This comes as oil prices continue to hover at around $100 a barrel, posing a significant problem for airlines that need jet fuel to stay operational. Airlines such as Delta, Air Canada, KLM, and Lufthansa have all canceled less popular routes to increase jet fuel use. Despite reporting higher profits than a year ago, United Airlines cut its full-year earnings outlook from $11 to $7 per share due to the oil crisis.