Apple has grown its production capacity for the AirPods, but it’s still failing to meet demand. CEO Tim Cook talked about the situation with its wireless earbuds during the company’s Q3 2017 earnings call. Cook explained how it has increased production capacity, but due to significant demand, the increase hasn’t been enough.

We’re also seeing incredible enthusiasm for AirPods. 98 percent customer satisfaction based on Creative Strategy’s survey. We have increased production capacity for AirPods and are working very hard to get them to customers as quickly as we can, but we are still not able to meet the strong level of demand.
– Cook

It can take over a month for units to ship out in the United States and the AirPods have been difficult to purchase since their release last year.