By Echo Wang

(Reuters) - The S&P 500 index closed at a record high on Monday, its fourth straight session of gains, as strong U.S. retail sales underscored economic strength and eased worries from Omicron-driven flight cancellations that hit travel stocks.

The rally is the longest since an eight-day streak that ended on November 8.

Holiday season retail sales rose 8.5 percent from November 1 to December 24, powered by an e-commerce boom, according to a Mastercard Inc. report, which helped the S&P 500 retailing index gain on the session.

Travel-related stocks, typically sensitive to coronavirus news, declined after U.S. airlines canceled about 800 more flights on Monday after nixing thousands of flights during the Christmas weekend, as Omicron cases soared.

The S&P 1500 airlines index declined. Cruise operators Norwegian Cruise Line Holdings, Royal Caribbean, and Carnival Corp all fell, leading declines on the benchmark S&P 500.

"The market is in this interesting place where we have a strong consumer, with spending up eight percent year over year. Personal consumption makes up 70 percent of our GDP, and that remains flush," said Sylvia Jablonski Kampaktsis, chief investment officer and co-founder at Defiance ETFs in New York.

"Omicron reminds us that we still exist in this corona ecosystem. And it'll probably be one of many things that we will continue talking about with this virus but the doomsday COVID scenario of 2020 feels like it's far behind us."

Monday's climb marks a fourth straight session of gains for Wall Street's main stock indexes after encouraging news last week related to the Omicron variant eased worries about the strain's economic impact.

All 11 main S&P 500 sector indexes advanced, with energy and tech leading percentage gains.

According to preliminary data, the S&P 500 gained 65.21 points, or 1.39 percent, to end at 4,791.00 points, while the Nasdaq Composite gained 216.53 points, or 1.38 percent, to 15,869.90. The Dow Jones Industrial Average rose 350.63 points, or 0.98 percent, to 36,301.19.

The Nasdaq Composite got a boost from megacap companies, including Tesla Inc, Microsoft Corp, Apple Inc and Meta Platform.

Main U.S. stock indexes are on track for a third straight yearly gain, with the benchmark S&P 500 set for its best three-year performance since 1999.

(Reporting by Echo Wang in Taos, New Mexico; Additional reporting by Medha Singh and Anisha Sircar in Bengaluru; Editing by Uttaresh.V and Richard Chang)