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As far as I understand, before the availability of GPS and other GNSSes, airplanes crossing large distances over water, beyond the range of ground-based navigation aids such as VORs and NDBs, largely used a combination of magnetic navigation and dead reckoning (whether manually or via an IRS).

This seems to have worked reasonably well – with the exception of some very high profile incidents such as the shootdown of Korean Air Lines 007.

Why weren't available phase comparison or time-of-arrival systems such as Omega (introduced 10 years before KAL007) or Loran-C used more widely by airliners?

Or were they, but just not uniformly and ubiquitously (at least not on that particular flight, as far as I can tell from the reports)?

Note: This question originally contained a sub-question on NDBs, which is now separate: What limits automated direction finding from working over oceans?

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    $\begingroup$ Note that Korean Air Lines 007 was equipped with an Inertial Navigation System, it was just used incorrectly on that flight. $\endgroup$
    – Bianfable
    Commented Jun 4 at 14:06
  • $\begingroup$ True, but having external navaids available could have helped spot that incorrect usage via cross-checking, right? That's why modern FMSes use a combination of all available position sources (GNSSes, ground-based navaids, INSes), is my understanding. $\endgroup$
    – lxgr
    Commented Jun 4 at 14:12
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    $\begingroup$ Do you really want to "lump" in "manual" dead reckoning with IRS/INS? Those are two radically different things. Once you have a sophisticated way to precisely measure every acceleration, I'd say that you are no longer in the realm of "dead reckoning". Sure, both concepts involve integration, but integrating precisely measured accelerations is a lot different than integrating estimated velocities. $\endgroup$
    – quiet flyer
    Commented Jun 4 at 14:34
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    $\begingroup$ The crew of KAL 007 believed that they were on course, because the needles were centered. Having a LORAN or OMEGA or GPS input into their navigation solution wouldn't have changed anything, because the waypoint to which they were navigating wasn't the one they should have been flying to. While we can Monday-Morning-Quarterback things all day long & decide that "if only they'd crosschecked {something} then the accident wouldn't have happened", it doesn't accomplish very much. $\endgroup$
    – Ralph J ♦
    Commented Jun 4 at 15:21
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    $\begingroup$ "does that also apply to VLF propagation", yes VLF (mostly) propagate using a tunnel between the D-layer and the ground. Of course the signal can be averaged on a long period to cancel or at least minimize the error. $\endgroup$
    – mins
    Commented Jun 4 at 15:37

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The Omega system was widely used by the airlines, but it was inaccurate, often by many miles. It main purpose was to get you close enough to land to start using more conventional radio navigation systems. I worked on them in the 1990s.

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