iPhone X shipping estimates continue to improve, with the flagship smartphone now available with free next-day delivery from Apple's online store if ordered by 3:00 p.m. local time today in the United States.

Apple quotes delivery by tomorrow for all iPhone X models except the silver SIM-free version with 64GB of storage, which is estimated for delivery within 2-4 days. This means every iPhone X is still a last-minute gift option.

Apple is also offering next-day delivery of all iPhone X models on its online store in the United Kingdom, and in some other countries, shipping estimates are short enough that delivery before Christmas may still be possible.

With next-day delivery now available, it would appear that Apple has achieved supply-demand balance of the iPhone X, at least for now.

Apple analyst Ming-Chi Kuo said improved iPhone X shipping estimates are the result of better-than-expected production, rather than weak demand. He originally predicted the iPhone X would likely remain in short supply until 2018.

Just hours after iPhone X pre-orders began in late October, Apple issued a statement to MacRumors indicating that customer demand was "off the charts."

We'll have to wait until Apple releases its next quarterly earnings results to analyze just how well the iPhone X has sold, but Apple's revenue guidance of $84-$87 billion suggests the smartphone's sales will be very strong.

iPhone X shipping estimates were initially pushed back to 5-6 weeks, but gradually shortened to just a few days by last week.

Apple always offers free next-day delivery of in-stock iPhone models, and it has extended the deal to all in-stock items ordered from its online store by 3 p.m. local time on Friday, December 22 in the United States.

Less-expensive gift ideas for an Apple fan available by Christmas include the Apple TV 4K, BeatsX, an official Apple-branded iPhone case, Apple Watch bands, or simply a physical or emailed Apple Store or Apple Music gift card.