Firefly Aerospace Inc. (FLY) had a pretty good Monday, with shares climbing over 14% on a combination of company-specific news and broader sector tailwinds that have space stocks flying high.

The Index Inclusion That Matters

The concrete news here is that Firefly Aerospace officially joined the Russell 2000 Index, which automatically triggered its addition to the broader Russell 3000 Index as well. The company was one of 18 firms selected for the Russell 2000 addition back in December, according to FTSE Russell.

Why does this matter? The Russell indexes are market capitalization-weighted benchmarks that institutional investors and fund managers watch religiously. FTSE Russell publishes these indexes to measure performance across different segments of global equity markets. When you get added to one of these indexes, you're suddenly on the radar of every fund that tracks it, which typically means increased buying pressure as those funds rebalance their holdings.

Riding the Space Wave

But that's not the whole story. Firefly shares also appear to be catching a boost from broader enthusiasm in the space sector. Space-related stocks have been trading higher lately thanks to a couple of big catalysts: news of a planned SpaceX IPO next year, and President Donald Trump's recent executive order titled "Ensuring American Space Superiority," which outlines ambitious U.S. plans for lunar and Mars exploration.

When the space sector gets hot, companies like Firefly tend to move together as investors get excited about the industry's growth prospects. It's the classic rising-tide-lifts-all-boats phenomenon, and Firefly is definitely getting lifted today.

FLY Price Action: At the time of writing, Firefly shares were trading 14.32% higher at $28.19, according to market data.