Chicharrero
Individual countries control their own airspace as a soveriegn right. They can, and do, make entry into that airspace subject to sertain conditions. The US has imposed very strict rules for all aircraft - foreign or US - entering its areas.
In UK we have made it a requirement for aircraft in UK airspace to have locked flight deck doors - irrespective of the country of registration - whether they are transitting or landing in the UK.
Anne
