International Airspace
Many pilots do not realize that the USA charges fees for the use of its airspace. The reason most pilots never see a bill is because the FAA will not charge aircraft that either depart from, or land at, a USA airport. In addition, if the total amount to be billed does not exceed $ 400 USD, the FAA simply ignores the invoice. The fees are calculated based on the Great Circle Distance (GCD) from point of entry into and point of exit from USA controlled airspace. The amounts are $61.75 per 100 Nm for enroute airspace (over the US) and $ 26.51 per 100 Nm for oceanic airspace (over the water). Consult the Overflight Fees page of the FAA website for details.

Why is this relevant? Well, the USA controls huge amounts of airspace off its east coast which extends well down into the Caribbean. So, if you fly from Miami to The Bahamas and then form The Bahamas to the Dominican Republic, that second flight is liable for airspace fees. Why?, because you flew through USA controlled airspace and you neither departed from, nor landed at, an airport in the USA. However, since the distances are short, the invoice amount will likely not reach the $400 limit and you will never see an invoice. However, if you make multiple flights to/from The Bahamas or continue down into the Caribbean, you may eventually hit that $400 mark and presto, an invoice form the FAA!

Most other countries also charge for the use of their airspace. The methods and fees vary widely. Some countries will exempt aircraft with a Maximum Takeoff Weight (MTOW) less than 12,500 lbs whereas others do not. Additionally, many countries also require that you obtain an overflight permit and/or landing permit in advance in order to fly over their country or to land in their country. If you want to fly within a foreign country, you may also require an Entry or Circulation permit to legally fly within the country. Beware of those who tell you stories of what it was like "a few years ago" because regulations are constantly changing and you don't want to be unceremoniously parted from the use of your aircraft in a foreign country. 

If you would like to learn a little more, we have published a number of articles including one on this topic which can be read here.

2 Replies
Thank you, Richard for sharing this, and for the link!  It is important to understand airspace and ATS on a larger scale.
You are most welcome, glad to do it!!