By Saturday morning, the ship date for iPad pre-orders, originally set to guarantee delivery by April 3, had been pushed back to Tuesday April 12.

Customers who had already pre-ordered are still scheduled to get their iPads next Saturday.

Meanwhile, the option to reserve an iPad for pick-up at an Apple Store has disappeared from Apple.com entirely.

That does not mean that there will no iPads available for sale next Saturday. Customers who reserved them over the past two weeks were told at the time that their iPads could be picked up between 9 a.m. and 3 p.m. Saturday April 3. After 3 p.m., any iPads that haven’t been collected may be made available, while supplies last, on a first-come, first-served basis.

It’s not clear whether the shortfall is due to strong demand, short supply or both.

Published estimates of the number of iPads Apple was expected to have on hand by April 3 range from a high of 1 million to a low of 300,000.

By Friday, according to the best available estimate, 240,000 iPads had been pre-ordered online. The only published report on reservations suggests that they’ve been coming in at roughly the same rate.

Kudos to the folks at Planet iPad, who were the first to spot the change in ship dates.

See also:

• iPad week two: 240,000 pre-orders
• iPad week one: 190,000 pre-orders
• Day 1 estimate: 120,000 iPad sales
• Apple sells 50,000 iPads in two hours
• The wild iPad Ruckus begins
• How many iPads will Apple sell?

[Follow Philip Elmer-DeWitt on Twitter @philiped]