National parks can fill up fast. The demand is so high that many of the country’s most popular parks require reservations, particularly during their peak summer months. To help regulate visitors, Montana’s Glacier National Park recently launched a new reservation system limiting the number of cars that can access its famous Going-to-the-Sun-Road in a given day — and tickets for June sold out in a matter of minutes.

According to Associated Press (AP), the park instantly received more than 10,000 requests for tickets to the mountain pass, which cost $2 on top of a standard park pass. Tickets are only required for vehicles, rather than those looking to enter on foot or by bike, and they’re not necessary for visitors who’ve made reservations within the park, such as lodging, camping, or guided tours. Only a few hundred cars are currently allowed per day as the 50-mile road is partially closed, but that number is expected to increase to roughly 4,600 when it reopens in full.

Flattered as the park must be, officials also recognize that it’s not sustainable for tickets to sell out so quickly. “This is our first year implementing this system, so we know that there are going to need to be tweaks,” Gina Kerzman, the park’s public information officer, told AP. Kerzman added that the park would be “monitoring the number of tickets versus the number of vehicles entering” to “adjust those numbers if we feel there is room for additional capacity.”

Though it remains unclear when Going-to-the-Sun-Road will fully reopen, the park intends to allow as many visitors as possible without compromising its protected land or the experience of its guests. Even so, we wouldn’t sleep on that reservation — it’s Glacier’s hottest commodity.