Following a rare firmware update for the AirPort Express, AirPort Extreme, and AirPort Time Capsule earlier this week, a few readers have contacted us about the Wi-Fi base stations being out of stock at their local Apple retail stores in the United States.

Specifically, the tipsters informed us that the AirPort Extreme was out of stock at the Apple Store, Sagemore location in Marlton, New Jersey, an outer suburb of Philadelphia, and the Apple Store, Beverly Center location in Los Angeles, California.

"I was trying to buy an AirPort Extreme today from the Beverly Hills Apple Store and an employee told me that Apple had asked for all of them back from all the stores," wrote one anonymous tipster.

To verify the tipster's claim, we contacted an Apple support representative who confirmed that Apple has pulled AirPort Extreme and AirPort Time Capsule stock from all U.S. stores. The base stations remain available to order online, while it appears the smaller AirPort Express can still be purchased both online and in stores at present time.

Apple's web-based Personal Pickup tool has also been removed from the AirPort Extreme and Time Capsule product pages on its U.S. storefront.

Even though Apple has pulled all AirPort Extreme and Time Capsule stock from U.S. stores, it is possible that select locations may still some units available. The base stations also remain on sale through authorized resellers such as Best Buy.

A retail source informed us that the AirPort Extreme and AirPort Time Capsule remain in stock at stores in the U.K., as confirmed by Personal Pickup, and the Wi-Fi base stations are also currently available at most stores in Australia, Canada, and Europe, so the in-store outage appears to be limited to U.S. stores for now.

With WWDC 2016 around the corner, scarce availability of the AirPort Extreme and Time Capsule in the U.S. will naturally stir speculation about a possible refresh to its Wi-Fi base station lineup. However, the stock outage could be related to the recent firmware update, Apple Store renovations, or regular fluctuations within Apple's inventory channels. There are also no rumors about an impending AirPort refresh.

Apple last updated the AirPort Extreme and AirPort Time Capsule at WWDC 2013 with faster 802.11ac Wi-Fi, new designs, and other internal changes. The slimmer AirPort Express was last updated in June 2012, drawing on the design of the Apple TV and gaining simultaneous dual-band 802.11n connectivity.

Given the lack of rumors, it is unknown what features a next-generation AirPort Extreme could have, but 802.11ac wave 2 Wi-Fi is a possibility. Some readers also speculate that Apple could integrate Siri features into the AirPort Extreme amid rumors it is working on an Amazon Echo competitor -- which could also be a new Apple TV.

Apple's AirPort base stations are designed to create or expand Wi-Fi networks, providing dual-band connectivity in addition to other features like music playback, wireless printing, and wireless backups. Read our AirPort roundup to learn more.

Update: Apple may be complying with an FCC deadline of June 2, 2016 related to router software security rules gradually phased in since 2014, which would explain why the stock outage is limited to U.S. stores.

"Starting June 2, 2016, permissive changes will not be permitted for devices approved under the old rules, unless they meet the requirements of the new rules," the FCC writes. "All devices partially or completely approved under the old rules cannot be marketed starting June 2, 2016 unless they meet the requirements of the new rules in all the bands of operation."

Update 6/2: Apple's AirPort base stations are once again available for Personal Pickup and are in stock at most retail locations in the United States, suggesting the stock shortage was a temporary blip that has now been resolved.

(Thanks, Cole, Justin, and Corrode!)