SpaceX has provided a rare update on its Seattle-centric plans to develop a multibillion-dollar Internet satellite network, saying that the work is now at a “critical stage.”

That assessment is part of the company’s argument against giving away the bandwidth required for such a network for another purpose – specifically, for 5G mobile broadband services that would be offered by Dish Network and other members of an industry coalition.

The Multi-Channel Video Distribution and Data Service Coalition filed a petition on Wednesday with the Federal Communications Commission on Wednesday, asking that the Ku-band spectrum currently being reserved for satellite broadband should be reallocated for 5G services.

“There is simply no basis to jeopardize 5G deployment to give additional spectrum to a speculative NGSO (non-geostationary orbit) service that already has access to ample spectrum,” the MVDDS Coalition told the FCC.

https://www.youtube.com/watch?v=t3qcDW3xkg4

The coalition said the bandwidth reserved between 12.2 and 12.7 GHz was just sitting unused, and that it could use the spectrum instead to provide “faster speeds, enhanced connection ublquity and truly real-time services and applications” to 5G customers.

That brought a quick response from SpaceX as well as from Intelsat, one of the partners in a competing Internet satellite venture led by OneWeb. Intelsat told the FCC that OneWeb already has a pending FCC application seeking access to the reserved frequencies, and that the bandwidth “will not lie fallow.”

Another satellite operator, SES, said it plans to use the bandwidth as well and was “alarmed by the prospect” that it might be reallocated.

The petition comes at precisely the wrong time.

In her filing, SpaceX’s Patricia Cooper wrote that the coalition’s request “comes at precisely the wrong time, given the ongoing, active investment and technological developments” relating to Internet satellite services.

Seventeen months ago, SpaceX unveiled its plans to develop a multibillion-dollar Internet satellite network, with much of the work being done at offices in Redmond, Wash. Since then, the company hasn’t said much about how things are going. In fact, SpaceX President Gwynne Shotwell said last October that the satellite plan was “actually very speculative at this point.”

OneWeb has taken a higher profile: One of the partners in the venture is Airbus Defense and Space, which is gearing up to build hundreds of small satellites that would be launched into low Earth orbit starting in late 2017 or early 2018. In April, OneWeb Satellites said it would build a satellite manufacturing facility near NASA’s Kennedy Space Center in Florida. And just last week, the company announced that it had signed supply contracts with MacDonald, Dettwiler and Associates in Canada, Sodern in France and Teledyne Defense in Britain.

Although SpaceX has downplayed its plans, there are ample signs of activity. For instance, plane-watchers noted last month that the company’s billionaire founder, Elon Musk, made a quick stopover in the Seattle area – presumably to visit the Redmond office. (SpaceX provided no information about the visit.)

.@SpaceX's Elon Musk departs PAE tonight in his new G650ER. pic.twitter.com/i1wnfAtrsd — Chris Edwards (@AeroimagesChris) May 7, 2016

Musk has said that as many as 1,000 employees could eventually be working at the Redmond office, with many of them engaged in the satellite project. SpaceX’s website currently lists more than 60 staff positions and internships to be filled in Redmond and Seattle. And last month, the Puget Sound Business Journal quoted SpaceX spokesman John Taylor as saying the Redmond operation was “making progress.”

Cooper’s filing for SpaceX puts a stronger spin on the operation – and also explains why the company is playing its cards close to the vest.

“It comes as no surprise that the details of these proposed NGSO FSS (fixed satellite service) are not currently well-known,” Cooper wrote, “as the development and deployment of satellite systems are highly proprietary and may take several years to finalize, during which time the operators hold details as highly confidential for obvious competitive reasons.”

Further details may soon come out in the open: In a document filed with the FCC a year ago, SpaceX said it would begin conducting satellite experiments this year. That was before a Falcon 9 rocket failure led to a months-long suspension of the company’s launch schedule. Despite that setback, it’s still possible for the first test satellites to go up as secondary payloads as early as next month, when SpaceX starts launching Iridium Next satellites from Vandenburg Air Force Base in California.