NASA says we’ll have to wait until 2019 to see the first orbital tests of the space taxis that are being built by SpaceX and Boeing for trips to the International Space Station.

The schedule shift was laid out Thursday in an online update.

SpaceX had scheduled the first uncrewed flight of its Dragon V2 spaceship for as early as next month. The revised schedule calls for that test flight, known as Demo-1, to launch next January.

NASA said it’s working with SpaceX to bring the Dragon hardware and associated activities to full readiness for Demo-1 in December, but is scheduling the launch in January to accommodate docking opportunities at the space station.

In a statement, SpaceX said a target date for Demo-1’s liftoff from Launch Complex 39A at NASA’s Kennedy Space Center would soon be set.

“Having completed a number of additional milestones including substantial training and numerous integrated mission simulations, end-to-end Dragon checkouts at the Cape, complete Falcon 9 vehicle integration review, and installation of the crew access arm at LC-39A, SpaceX is on track for launch readiness in December. “We look forward to launching our first demonstration flight of Crew Dragon — one of the safest, most-advanced human spaceflight systems ever built — as part of the Commercial Crew program and working with NASA to identify the specific launch target date soon.”

The Demo-2 crewed flight would follow in June 2019, with NASA astronauts Robert Behnken and Doug Hurley visiting the space station.

Boeing’s uncrewed flight test for its CST-100 Starliner capsule had been set for late this year or early next year. Now it’s due to launch no earlier than next March.

That test flight would be followed by a crewed flight test next August. So far, three crew members have been chosen for that mission to the space station: NASA astronauts Eric Boe and Nicole Aunapu Mann — plus Boeing test pilot Chris Ferguson, who served as the commander for the final space shuttle mission in 2011.

It wouldn’t be surprising if further delays crop up as the dates for first flights approach.

After each company successfully completes its crewed test flight, NASA will begin the process of certifying the spacecraft and systems for operational crew missions to the space station.

In the past, NASA has suggested that the scope of Boeing’s crewed test flight could be expanded to serve as the first operational space taxi mission. This week’s revised schedule leaves open that possibility. It sets next August as the “anticipated readiness date” for the first operational mission, with the second operational mission following in December 2019.

The agency has contracted with each company for six missions, with NASA selecting four astronauts to fly on each mission. “We’ve got five seats on the Starliner — four for the NASA astronauts, one extra,” Boeing CEO Dennis Muilenburg said during this week’s GeekWire Summit.

Both SpaceX and Boeing would be allowed to sell their extra spots to paying passengers with NASA’s OK.

“If Boeing and SpaceX have a spaceflight participant that they want to put on one of our flights, they propose that to NASA, we evaluate it … We’ve got to make sure that the space station can accommodate it. But the contractual ability to do that is there,” NASA’s Phil McAlister said in June during the Space Frontier Foundation’s NewSpace conference in Renton, Wash.

The competition between SpaceX and Boeing for space taxi services got some additional attention this week: A series of reports linked the wide circulation of a newspaper op-ed article critical of SpaceX’s pre-launch “load and go” procedure to a Washington public relations firm with Boeing connections.

The first report was published by Ars Technica on Thursday, with a follow-up from Business Insider today.

Update for 5:36 p.m. PT Oct. 5: This report has been updated with SpaceX’s statement.