Oil will flow unimpeded into the Gulf during the cap switch for at least part of the weekend.
If all goes according to plan, the combination of the cap and the new vessel could collect all the leaking oil by Monday. Work continues on what officials hope will be the ultimate solution: a pair of relief wells intercepting the leaking well far below the seafloor.
The new containment cap is expected to form a better seal over the well head, to allow more of the oil to be collected and sent up to ships on the surface for collection or burning.
"Technically it's pretty achievable," Allen said. He said if the new cap can't be placed on the well, the old cap will be put back and there are multiple backup caps available in case any one cap fails.
The new, tighter cap should be in place early Monday. Allen said the ship Helix Producer, which is to be hooked to a different part of the leaking well -- lower than the new cap -- will start collecting oil Sunday and be fully operational Tuesday. He has previously said that the full system should be able to collect 60,000 to 80,000 barrels a day.
The schedule for both efforts has been accelerated to take advantage of what could be a rare window of good weather. The hookup of the Helix Producer was delayed this week by poor weather.
The containment effort is not the permanent solution to stop the environmental catastrophe that began April 20 when the Deepwater Horizon oil rig exploded, killing 11 workers.
Still, the best hope to stop the spewing oil from the blown-out well a mile under the sea is the drilling of relief wells deep below the seafloor. Though officials said the first could be finished by the end of July, weeks ahead of schedule, they are quick to point out that such an optimistic timetable would require ideal conditions every step of the way.
That is something that has rarely happened since the leak began.