Delays earlier this week have set up a weekend of rapid-fire Florida launches, weather permitting, starting with a United Launch Alliance Delta 4 Heavy flight Saturday and possibly two SpaceX flights Sunday just nine hours apart that would mark the company’s 100th and 101st orbital missions.

If SpaceX presses ahead and both rockets get off — and the weather is not ideal — it would mark the shortest span between two U.S. orbit-class missions since 1966.

But ULA has priority with plans to launch a powerful Delta 4 Heavy, one of just five left in the company’s inventory, early Saturday to boost a National Reconnaissance Office spy satellite into orbit.

A triple-core Delta 4 Heavy, one of only five left in ULA’s inventory, stands poised for launch early Saturday on a flight to put a National Reconnaissance Office spy satellite into orbit.

William Harwood/CBS News

With forecasters predicting an 80 percent chance of good weather, liftoff from pad 37 at the Cape Canaveral Air Force Station is targeted for 2:04 a.m. EDT Saturday.

ULA originally planned to launch the national security mission Wednesday, clearing the way for SpaceX to launch a previously flown Falcon 9 rocket from nearby complex 40 on Friday evening to place Argentina’s SAOCOM 1B remote-sensing satellite into a polar orbit.

The California rocket builder then planned to launch the company’s 12th batch of Starlink internet relay satellites from pad 39A at the Kennedy Space Center Saturday morning. That flight later moved to Sunday.

The Delta 4 launch then was delayed one day at the request of the NRO and then again to Saturday because of technical problems that cropped up during a launch attempt early Thursday.

That set up the possibility of both SpaceX launches on Sunday. Air Force launch weather forecasts and off-shore warnings indicated the Starlink flight was tentatively targeted for launch from pad 39A at 10:08 a.m. Sunday with the SAOCOM 1B launching from pad 40 at 7:18 p.m.

The SAOCOM-1B launching will be the first since 1969 to follow a southerly trajectory toward an orbit around Earth’s poles.

But the weather could pose problems. The 45th Space Wing forecast Friday called for a 50 percent chance of acceptable conditions Sunday morning, declining to 40 percent that evening.