RKLB, ASTS, TDG: Insiders are Selling These 3 Space Stocks

Key Points

• Rocket Lab’s heavy insider selling looks less alarming because nearly all sales came through a prearranged trading plan.
• AST SpaceMobile faces the most concerning signal after American Tower cut its stake by nearly half in discretionary sales.
• TransDigm’s insider selling is sizable but limited to one director, making it only a modest bearish indicator.

Some of the most talked-about space stocks among retail investors have seen recent bouts of insider selling. Below, we’ll detail the selling surrounding Rocket Lab NASDAQ: RKLB and AST SpaceMobile NASDAQ: ASTS. Additionally, we’ll examine the insider sales of a name that—while not a retail darling—is a stalwart of the aerospace industry, Transdigm NYSE: TDG.

RKLB CEO Sells Over $150 Million Worth of Shares

First up is Rocket Lab, which has surged by approximately 177% in 2025. The stock has seen significant insider selling in December, largely from the firm's founder and CEO, Peter Beck. In December, Beck’s total sales amounted to around $141 million. 

The company also saw sales from its Lead Independent Director, Merline Saintil. In comparison to Beck’s sales, though, Saintil’s were small, totaling around $1.7 million.

This isn’t the only critical difference between the two sales. All of Beck’s sales came under a predetermined 105b-1 plan. As insiders must determine the timing of these sales well in advance of when they happen, 105b-1 sales don’t provide a strong near-term bearish signal.

Around $1.43 million of Saintil’s sales were not made under a predetermined plan. While that introduces a slightly more cautionary signal, the dollar amount is modest relative to Beck’s sales and Rocket Lab’s market capitalization.

Although the insider selling at Rocket Lab appears concerning, because almost all of this selling was conducted through a 10b5-1 plan, it doesn't necessarily signal future downside. 

Big-Name Shareholder Cuts ASTS Position Nearly in Half

Despite seeing significant ups and downs in 2025, AST SpaceMobile’s shares have gained mightily, up more than 250% on the year. 

American Tower NYSE: AMT, one of the world’s largest owners and operators of telecommunications real estate, is a majority shareholder of ASTS stock. American Tower recently made a sale amounting to just under $160 million, dwarfing the size of any insider sale ASTS has seen before. These sales did not come under a predetermined plan, amplifying their potential bearish implications.

American Tower owns both Class A and Class B shares of AST SpaceMobile, with Class B shares convertible into Class A on a one-for-one basis.

Before the sale, the company held approximately 2.5 million Class A shares and 2.17 million Class B shares, for a combined effective position of 4.67 million shares.

Following the sale of roughly 2.29 million Class A shares, American Tower’s effective stake dropped to about 2.38 million shares. In total, this represents a 49% reduction in its AST SpaceMobile position.

Given American Tower’s deep expertise in telecommunications infrastructure, the scale and discretionary nature of this sale stand out. It is difficult to ignore the implication that a highly informed strategic investor chose to materially reduce exposure after the stock’s dramatic run.

TDG Insider Ups Sales Big Time in December

Transdigm is a key company in the commercial aerospace supply chain, providing essential parts to firms like Boeing NYSE: BA. Compared to the rest of its industry, Transdigm has an astoundingly high gross margin of around 60%.

This demonstrates the significant pricing power the stock has over its customers. Despite providing a return of only around 8% in 2025, the stock’s return over the past three years is around 147%.

In December, Transdigm insiders have sold approximately $157 million thus far. Notably, around $127 million of this selling was from Robert Small, a member of the firm's Board of Directors, and did not come under a 105b-1 plan. 

It's certainly not a good sign to see an insider making such large discretionary sales.

However, outside of CEO Michael Lissman’s small $2.6 million sale in November, Small appears to be the only TDG insider making significant discretionary sales recently. As these sales are largely isolated to one individual, they are only a slightly bearish signal for Transdigm.

American Tower’s ASTS Sale: A Red Flag Going Forward

When comparing insider activity across these three stocks, AST SpaceMobile clearly raises the biggest red flag. Rocket Lab’s sales are overwhelmingly preplanned, and TransDigm’s selling is concentrated in a single board member. In contrast, American Tower’s large, discretionary reduction in AST SpaceMobile exposure carries far more informational weight.

Given American Tower’s stature and industry insight, investors would be wise to pay close attention. While insider selling alone should never dictate an investment decision, the scale and nature of this transaction suggest a materially more cautious outlook for AST SpaceMobile going forward.