Form 144 at Space Companies: Insider Sale Notices Decoded

A Form 144 is the notice an insider files with the SEC when they place an order to sell restricted or control shares, so it can appear on the day of the sale, two days before the matching Form 4. In the 30 days to October 12, 2026, I counted 19 Form 144s from 12 of 18 listed space and satellite companies I checked, led by a notice for 342,170 SpaceX shares worth about $52 million on September 22. A Form 144 shows a planned sale; the Form 4 that follows shows what was sold. This is research, not financial advice.

What a Form 144 is, and when it is filed#

Under Rule 144 (17 CFR 230.144), an insider of a reporting company who sells more than 5,000 shares, or more than $50,000, in any three months must file a Form 144 electronically. The rule says the form is transmitted "concurrently with either the placing with a broker of an order to execute a sale" or the direct execution of the sale. In practice the notice appears on EDGAR on the day the order is placed.

That timing is what makes it useful. A Form 4 is due before the end of the second business day after a trade, so a Form 144 can tell you about a sale a day or two earlier. Rule 144 also covers affiliates and holders of restricted stock who are not Section 16 insiders, so the notice can reveal sales that a Form 4 never would.

Form 144 versus Form 4#

Because the value on a Form 144 is an estimate at filing, expect small differences from the Form 4. In the three cases I cross-checked, the share counts matched exactly.

Form 144 filings at space companies, 30 days to October 12, 2026#

I read every Form 144 filed from September 12 to October 12, 2026 by 18 listed space and satellite companies (Rocket Lab, AST SpaceMobile, Intuitive Machines, Planet, Redwire, BlackSky, Firefly, Voyager, Virgin Galactic, Globalstar, Iridium, Viasat, Karman, Spire, SpaceX, HawkEye 360, Applied Aerospace & Defense and York Space Systems) from EDGAR. Twelve of them filed at least one. The ten largest:

The remaining nine notices were smaller, from officers or directors at BlackSky, Globalstar, HawkEye 360, Iridium, Planet, Spire and Viasat, each under about $0.5 million. Dates are the filing dates; values are the estimates stated on each form.

Reading one end to end: SpaceX, September 22#

• Form 144, filed September 22: Gwynne Shotwell, listed as director and officer, gave notice of a sale of 342,170 shares with an estimated value of about $52.0 million.
• Form 4, filed September 24: it reports five sale lines on September 22 totalling 342,170 shares at weighted-average prices from about $151.15 to $154.72, and footnotes that the sales were made under a Rule 10b5-1 trading plan adopted on June 23, 2026.
• What to take from it: the Form 144 gave the share count two days before the Form 4 gave the prices, and the Form 4 said it was a pre-arranged plan sale. Our Form 4 guide explains why that distinction matters.

The same pattern holds for Rocket Lab's CFO (140,157 shares on October 1, under a 10b5-1 plan) and AST SpaceMobile's CTO (40,000 shares on September 16).

How to read a Form 144#

1. Check the filer and role. An officer, a director, a trust tied to one, or a fund with more than 10% each mean something different. The Redwire notice came from a fund entity, not an executive.
2. Size the sale. The form lists the company's shares outstanding; check the shares sold against that and against what the seller still holds in their latest Form 4.
3. Look for a 10b5-1 plan date. A plan adopted months earlier is weak evidence about the insider's current view.
4. Wait for the Form 4. It gives the real prices and codes.
5. Check the lock-up. After an IPO, notices cluster around release dates; our space IPO lock-up calendar lists them.

Following insider notices on Martian Alpha#

Martian Alpha's free catalyst feed lists events for listed space stocks, including an "Insider Trade" category, and the Insider Transactions page on the Space Professional plan lists Form 4 trades for tracked US space stocks with the codes labelled. A free account adds a watchlist (2 tickers) with news alerts. Form 144 notices themselves are on EDGAR; Martian Alpha does not list them separately.

FAQ#

What is a Form 144?#

A notice to the SEC that an insider plans to sell restricted or control securities under Rule 144. It is filed when the sell order is placed and lists the shares, an estimated value and the approximate sale date.

Does a Form 144 mean the insider will sell?#

It is a notice of a proposed sale made at the time the order is placed, so a sale is intended, but the Form 4 confirms what actually traded and at what price.

Is a Form 144 bearish for a stock?#

Not on its own. Many notices relate to plan sales, tax needs or diversification, and a single notice is a small piece of evidence. Look at the seller's role, the size against their holding and any 10b5-1 plan.

What is the difference between Form 144 and Form 4?#

Form 144 announces a proposed sale when the order is placed; Form 4 reports the completed trade within two business days, with the actual price and transaction code.

How many Form 144s did space companies file recently?#

In the 30 days to October 12, 2026, 19 notices from 12 of the 18 listed space and satellite companies I checked, the largest for about $52 million at SpaceX.

Sources#

• 17 CFR 230.144, Persons deemed not to be engaged in a distribution (Cornell LII), including paragraph (h) on Form 144 notice.
• SEC Form 144.
• EDGAR submissions and Form 144 filings for the 18 companies, September 12 to October 12, 2026, read October 12, 2026 (data.sec.gov); for example the Rocket Lab Form 144 filed October 1, 2026.
• SpaceX Form 4 for Gwynne Shotwell, filed September 24, 2026.
• Counts, the cut-off of about $0.5 million for the remaining notices, and the estimated values are my own tally of the forms.