United Airlines will begin flying seasonally to two more European destinations in the spring.

Daily nonstop service to Porto, Portugal and Reykjavik, Iceland starts May 4 and May 23, respectively, the airline said in a statement Tuesday.

In 2018, flights to those cities will continue until Oct. 3. United hasn't announced dates for subsequent years.

The eastbound Iceland flight from New Jersey is scheduled to last 5 hours, 40 minutes. The return trip is scheduled for 6 hours, 10 minutes.

Flight times to and from Portugal will be 7 hours, 5 minutes eastbound and 8 hours westbound.

In May, United added service between Newark and Buenos Aries, Argentina. Daily flights to the South American city begin Oct. 28.

United also announced it was adding a route from San Francisco to Zurich, Switzerland as well as service from Dulles Airport in the Washington D.C. area to Edinburgh, Scotland. Those flights begin next year.

Jeff Goldman may be reached at jeff_goldman@njadvancemedia.com. Follow him on Twitter @JeffSGoldman. Find NJ.com on Facebook.