U.S. holiday airfares are reaching decade highs as elevated jet fuel costs linked to the Iran war raise airline expenses and constrain capacity. Hopper forecasts average domestic round-trip fares of $402 for Thanksgiving, up $95 from last year, and $452 for Christmas, up $85. Domestic round-trip tickets are already 31% more expensive than during the comparable period last year, while existing estimates put Thanksgiving fares 31% higher and Christmas fares 23% higher. Jet fuel can account for up to 30% of airline operating costs and rose from about $99 a barrel before the war to $209 in April and $195 in mid-September, according to the International Air Transport Association. Brent crude briefly topped $101 a barrel before retreating to $97.83 on hopes of a U.S.-Iran deal and the reopening of the Strait of Hormuz. Airlines have raised fares and fees, reduced less-profitable routes and warned that price relief may lag any decline in fuel costs because schedules and tickets are set months in advance. Travelers can reduce costs by booking before Halloween, comparing destinations and avoiding peak travel dates around Thanksgiving and Christmas.