@Ann - Aircraft navigation
is extremely more complex than boats and ships. Commercial
started with DR and CN - like boats but soon directional radio
made electronic navigation possible. The purpose of aerial navigation is twofold - find where you are going in all kinds of weather
and separate airplanes going to the same place in a 3D airspace.
You understand, of course, there is only one shortest route
from New York
and they all wanna use it - both ways!
Long range over water
evolved into long rage radio
(LORAN) and assigning altitudes and departure times. There were still periods over water
where DR was used. When in range of radio again course errors were corrected with radio nav.
In the 1970s Inertial Navigation was created. The reason Lat/Long is posted on the gates at airports is to program the INS (Intertial Nav System) - gyroscopes and accelerometers would measure every movement from gate to arrival and position was calculated but they needed precise lat long starting points. While in range of radio nav (over land basically) INS position and speed could be theoretically updated. INS being mechanical drifted over time but was pretty good at finding continents.
INS joined radio nav in the cockpit
. GPS has now joined Radio Nav and INS. It took years and years and years for the FAA to approve GPS first for enroute nav and then for terminal and approach nav.
FANS is an acronym denoting "Future Air Navigation System." This a big bureaucracy defining standards for integration of nav systems. Also defining when nav systems differ in position, which one shoud the FMC (Flight Management Computer) trust.
As a side note - the Atlantic route
has always been tough - packing as many flights in as possible has always been a goal. Airplanes started using reporting transponders (think AIS) years ago. This allowed reduced vertical flight path separation and the trailing separation because in the middle of nowhere - aircraft could "see" and avoid each other.
So - ask a simple question and someone around here will give a complicated answer. Bottom line is that aircraft have multiple methods for navigation and actually rely on no one method and each method probably has multiple redundant backups.