Apologies if this has been hashed to death...
Please guide to the appropriate thread if needed.

Why does the transatlantic flight path of pretty much all flights look like an inverted U..well not exactly but if I look at the flight path and then look at the starting point and ending point of the flight, the first thing at I wonder is....why isnt the flight path straight? Will it not be a shorter flight if instead of going all way to Newfoundland...st. john and near Greenland you just leave the US coast at NY/VA and keep flying straight?
Is is because of the curvature of earth that flying closer to the equator takes longer
OR weather patterns
OR is it to prove the age old adage...the smallest distance between any two points is not always a straight line!

This is not quite the place to write a full explanation of map projections, and the distortions that occur when you try to show a sphere (which earth more-or-less is) on a flat surface -- and, indeed, my knowledge is too shallow to write one.

But most of the curvature is a result of that phenomenon. The true shortest distance between two points on earth will show on most map projections as an arc. (Hence the term "Great Circle Route" for the most direct line.) See http://gc.kls2.com/, or prove it for yourself with a globe and a piece of dental floss.

^^
Good answer.

When you use that site, if it still shows a flat map, choose "ortho" from the dropdown for "map style".

The GCM website ortho option clarified my doubts, but I am going to confirm it with some pushpins, thread and a globe!

Shame that I forgot high-school geometry!!

Something I tried which helped me to understand this very phenomenon:

Take a piece of string and a globe and drag the string between two points on the globe. When you pull the string taught it will naturally follow the shortest path which, counter-intuitive to us who grew up looking at flat maps, actually curves. I was surprised to find that the shortest path between Atlanta and Tokyo goes over Alaska.

Here's an example of something similar using a flat map:

http://maps.forum.nu/gm_flight_path.html

There are a number of polar routes. Take a look at EWR-SIN sometime.

Also note that depending on weather conditions and prevailing winds, a flight may not take the shortest "great circle" path. While ATL-NRT will typically fly well over Alaska, the reverse is not true. The eastbound flights route much farther south to take advantage of strong jetstream tailwinds.

Compare:
16 November - DL56 NRT-ATL
16 November - DL55 ATL-NRT

Here's another perspective: people sometimes use the term "on the other side of the world", right? well, that's what it really is. By going across the top of the earth, you are skipping the extra distance to go around. think of it as going from the centre of a circle to the top instead of going to the left, then up around the outline.

Gregmchicago posted an excellent explanation. Take this as a visual example, its EWR-SIN. http://gc.kls2.com/cgi-bin/gcmap?PATH=EWR-SIN