Simplify the following text for a Grade 11 native English-speaking person.
Original: Such flag days are standard throughout the United Kingdom , with the exception of Merchant Navy Day , ( 3 September ) , which is a specific flag day in Scotland during which the Red Ensign of the Merchant Navy may be flown on land in place of either the Saltire or Union Flag .
Simplified: These days are the same as the flag days of the United Kingdom with the exception of 3 September ( Merchant Navy Day ) , which is a specific flag day in Scotland and during which the Red Ensign may also be used .