Viasat (VSAT +4.19%) stock tumbled 18.1% through 11:05 a.m. ET Tuesday -- but perhaps not for the reason you think.

Yesterday, T-Mobile (TMUS -7.71%) announced a new direct-to-cell satellite communications service in partnership with SpaceX Starlink, which is roiling the space satellites market. The move threatens Viasat's business model (I think), and is probably a good reason to be leery of Viasat stock.

But that's not why investors are selling Viasat stock today. They're selling because insider shareholders are selling.

VSAT - Viasat

$61.47+$2.47 (+4.19%)

NASDAQ · As of 4:00 PM ET 10/23/26

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Key data points

Market capMarket cap calculated using publicly traded shares outstanding only. Does not include unlisted, private, or dual-class non-traded shares. Implied market cap may vary.$8.47B

Day's range$58.04 - $61.93

52wk range$29.13 - $93.03

Volume5.1M

Avg volume1.9M

Gross margin27.60%

Viasat's great Canadian (and Luxembourger) stock dump

As reported on the SEC's website last night, three major holders of Viasat stock have all filed notifications of significant stock sales:

• Luxembourg company Triton Luxtopholding Sarl announced the sale of 3.75 million shares of Viasat.
• The Ontario Teachers' Pension Plan Board announced the sale of an identical 3.75 million-share stake.
• Finally, CPP Investment Board Private Holdings, which, according to S&P Global Market Intelligence, is a subsidiary of the Canada Pension Plan Investment Board, is selling -- you guessed it -- 3.75 million shares.

In total, the three sales encompass 11.25 million shares of Viasat stock dumped on the market, which is about 8.8% of all Viasat stock outstanding. S&P Global notes that CPP, at least, is one of Viasat's five biggest shareholders, owning 8.5 million shares, and now we learn that it's selling roughly 44% of the Viasat shares it owns.

Is Viasat stock a sell?

Why are these three big holders of Viasat stock selling, and are the sales related? In the case of the Canadian insider sales by the Ontario and Canada pension plans, I have a sneaking suspicion that the sales are related -- but why some obscure Luxembourger investor is selling at the same time, and selling the exact same amount, remains a mystery.

I also suspect, but cannot prove, that the sales may indicate worry among these shareholders that the T-Mobile-plus-Starlink tie-up is a bigger threat to Viasat than other investors yet appreciate. If I were a shareholder in unprofitable Viasat stock, I think I'd be getting a little bit nervous today, too.