From the day it launched the iPhone 4 in June, Apple (AAPL) has ramping up production, trying to get supplies to the point where they could meet demand.

The company reached that point of retail equilibrium last week, when shipping delays in its online store, which had been listed at 3 weeks from June through September, finally shrank to 24 hours.

That should put Apple in good stead going into the holidays, writes Barclays’ Ben Reitzes in a note to clients issued Tuesday. He adds:

“Apple has now expanded distribution to Target (Target also sells the iPad) to join others including Apple stores, AT&T, Best Buy, Radio Shack and Wal-Mart. Perhaps more importantly, we believe availability is improving overseas, with the iPhone 4 set to ship for its first full quarter in China.”

Reitzes estimates that Apple will sell 14.8 million iPhones in the quarter (fiscal Q1 2011) that ends Christmas Day and, assuming that Verizon (VZ) gets the iPhone next year, 54 million in fiscal 2011.

[Follow Philip Elmer-DeWitt on Twitter @philiped]