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In this article about how the SpaceX anomaly will affect Iridium it says:

In its official website, Iridium describes itself as "the world's only truly global mobile satellite communications company." It offers global voice and data communications coverage.

Is Iridium the only mobile satellite communications network that has polar orbits, and therefore has line-of-sight service to satellite telephones at the poles?

Quote and screen shots from: https://www.iridium.com/company/companyprofile

Reaching across land, sea, and air, including the polar regions

Company Profile: The world's only truly global mobile satellite communications company

Image of a satellite

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    $\begingroup$ They have the brightest lighthouses in space. See Iridium flare $\endgroup$
    – Andreas
    Commented Oct 28, 2016 at 10:01

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As of today (October 2016), Iridium is the only public satcomm provider using a constellation of low earth orbit satellites with high inclination orbits to provide a service with global coverage. You can compare coverage easily on this website.

Iridium constellation (this image is from here)

Inmarsat and Thuraya in contrast use geostationary satellites, Thuraya uses spot beams to cover specific regions, while Inmarsat has wide beams. Globalstar uses low earth orbits, but the inclination of 52° does not allow to reach polar regions.

Military may have additional non-public networks. A non-public LEO/MEO constellation would not go unnoticed, as more than 30 spacecraft are needed depending on orbital height (Iridium uses 66 plus spares), so all LEO and MEO constellations tend to be known. Iridium is the only such constellation with continuous coverage of polar regions. This makes it unlikely, that military has a non-public network with coverage and latency comparable to Iridium.

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    $\begingroup$ You forgot ORBCOMM, but the inclination is lower than Globalstar, so... $\endgroup$
    – PearsonArtPhoto ♦
    Commented Oct 28, 2016 at 13:42
  • $\begingroup$ @PearsonArtPhoto And BGAN. I was surprised how many constellations exist. $\endgroup$
    – Andreas
    Commented Oct 28, 2016 at 13:52
  • $\begingroup$ Orbcomm was mentioned in a comment as a provider - realize that Orbcomm handles short-message data, not voice. $\endgroup$
    – mike65535
    Commented Oct 28, 2016 at 14:40
  • $\begingroup$ Communications in my mind includes data, voice, etc. The word "phone" or "voice" isn't mentioned in the included claim. $\endgroup$
    – PearsonArtPhoto ♦
    Commented Oct 28, 2016 at 15:17
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    $\begingroup$ @PearsonArtPhoto I think in this business "mobile" refers to people holding there phone type of thing. Orbcomm says they are M2M (machine-to-machine) which I think is more like distributed sensors and data collectors, that can cache and send in bursts during the next pass. "mobile" probably requires continuous coverage so people can update their Facebook or call someone in real time $\endgroup$
    – uhoh
    Commented Oct 28, 2016 at 15:54
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As explained on the Wikipedia page (https://en.wikipedia.org/wiki/Iridium_satellite_constellation), Iridium constellation uses polar orbits. Those orbits are intended for a full "north-south" coverage.

The downside of the Polar orbit is that each orbit has a shift in longitude. This issue is corrected by the use of 6 different polar orbits (equidistant) with each individual coverage overlapping the next one (see the GIF on the Wikipedia page).

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