Last day of trading before Christmas at the New York Stock Exchange (NYSE) in Manhattan, New York City

Stocks slightly higher as traders return from holiday

Stocks were modestly higher Monday in muted trading after the Christmas holiday, helped by big technology companies like Apple and Nvidia.

Trading is expected to be quiet, but potentially volatile, this week as the omicron coronavirus variant continues to spread quickly throughout the U.S. and overseas. However most big investors have closed out their positions for 2021, and are like to hold their ground until next week.

The S&P 500 index was up 0.9% as of 11 a.m. Eastern. The Dow Jones Industrial Average rose 0.6% and the technology-heavy Nasdaq rose 1.1%.

READ MORE: Omicron casts shadow over economy’s pandemic recovery

The S&P is on pace to close out the year up nearly 27%, a banner year for the stock market.

Last week, the S&P 500 set another record as fears ebbed about the potential impact of omicron outbreaks. However, much is still uncertain about the variant, which is spreading extremely quickly, leading to a return to pandemic restrictions in some places.

Hundreds of flights were cancelled in the U.S. over the holiday weekend, with airlines reporting COVID-related staffing problems. France reported more than 100,000 new cases in a daily record.

Airline stocks were down on the news, with Delta Air Lines, United Airlines and American Airlines all falling more than 2% in early trading.

Authorities in many countries have doubled down on vaccination efforts as omicron outbreaks complicate efforts stave off fresh lockdowns while hospitals are still under strain from delta variant infections.

Asian and European markets were either closed or mostly higher on Monday. London and Hong Kong were closed, while Japan’s stock market closed slightly higher.

In other international developments, the Turkish lira fell another 5% against the dollar. The currency has tumbled sharply this year as the Turkish government has tried to invigorate its economy despite chronically high inflation. The government announced a plan last week that would encourage Turks to put their money back into lira bank accounts to prop up the currency.