Two concepts that are really interesting are the earth’s ever changing magnetic field and its orbit around the sun as related to the moon. Each help to explain how true north varies from magnetic north and how a total solar eclipse can be seen on April 8, 2024 at around 3:30 pm at various locations around New England.  Ok, let’s take these one at a time.

Runway Designators that Change

A declination arrow to illustrate runway orientations. Black and white image.
The current westward declination at Eastport Municipal Airport in Eastport Maine is 15° 53’ W and anticipated to change by 0°7’ E per year.

Runway designators (or “numbers”) depict the magnetic orientation of a runway.  The runway number is the whole number nearest one‐tenth the magnetic azimuth of the centerline of the runway, measured clockwise from the magnetic north. They are numbered according to the points on a compass, from 1–36, reflecting the magnetic compass reading to the nearest 10 degrees and dropping the last digit. If an aircraft is sitting on the numbers on runway 36, then it’s facing north. Some great aviation movies use “the numbers” in key dramatic and comedic scenes. Movies such as Sully, Airplane, Pushing Tin, United 93, American Made, and One Six Right all depict pilots and air traffic controllers announcing runway designators over the radio. Aircraft navigation systems and instruments are calibrated to magnetic north rather than true north. When the earth’s magnetic field changes over time, magnetic north changes. According to Dr. Patrick Alken of the National Geophysical Data Center at NOAA, scientists don’t have a good understanding of why the magnetic field is changing and they say they can’t predict more then a few years ahead of time what the field do. So, airports change the runway numbers if the magnetic declination changes enough and the runway heading no longer corresponds to the nearest 10 degrees.  Geophysics concepts help you to understand that when you are watching the movie Pushing Tin and you hear the line “Sparta 753 turn left heading zero-seven-zero, maintain two-thousand till localizer. Cleared ILS runway four,” you might wonder is it still ILS runway four, or is it five?

Image of a runway end with the number "34" clearly visible.
A photo of Runway 34 at Portsmouth International Airport at Pease. | Photo: Andrew Brian Pomeroy

April 8, 2024 Solar Eclipse & Airports

Path of the eclipse.According to NASA, during the annular eclipse, the moon covers the sun but leaves an outside ring some call a “ring of fire” — it darkens the sky instead of plunging Earth into a night-like darkness, which is what happens during a total solar eclipse. A lunar eclipse – the appearance of a red moon – happens when the moon passes into the Earth’s shadow, according to NASA. So what’s coming in April is something we will not see again until August 23, 2044, a total solar eclipse.

Solar eclipses are rare in part because they can only occur during a new moon and when “the moon’s orbit is tilted five degrees to Earth’s orbit around the Sun,” according to the National Weather Service. On April 8 the shadow of the moon will travel at more than 1,500 miles per hour as it crosses the earth and over the course of about an hour, viewers in 15 states will experience up to four and half minutes of darkness when the moon moves fully in front of the sun, revealing the sun’s faint outer atmosphere. Seven of Hoyle Tanner’s airport clients will be in the line of totality and will experience what describes as “without a doubt, the greatest cosmic pageant that can be witnessed.”

A numerical chart illustrating seven of Hoyle Tanner's clients in the line of totality for the solar eclipse taking place on April 8th, 2024.

At each of these airports, an FAA Air Traffic Bulletin is issued and pilots are being advised to be aware and vigilant of possible delays/disruptions in the National Airspace System, due to extremely high volumes of air traffic anticipated during this event.  So if you are in northern Vermont, New Hampshire, or Maine around 3:25 pm and you have anywhere from 1 to 3 minutes to spare, grab a set of solar eclipse glasses and look up in the sky and witness the spectacle.

Now do you see how a total solar eclipse and the earth’s magnetic field conjure up thoughts of wonder, and marvel?


More information:

Events in Vermont:

Solar eclipse 2024 events planned in Vermont, including Burlington, St. Albans and ski resort celebrations | Vermont Public

Events in New Hampshire:

Total Solar Eclipse over New Hampshire on April 8, 2024 | Activities (

Events in Maine:

Solar Eclipse 2024 – Visit Maine