Hi, My Husband Noticed Two Very Dark Almost Black Bruises

Hi, my husband noticed two very dark almost black bruises on the back of my thigh, midway between my buttocks and knee, a day ago. I have just noticed the same happening on my other thigh, in almost the same area. I am a healthy 54 year old female. I have been on an 8 hour aeroplane trip in the last 5 days. I do have bad circulation problems but have been walking daily and did stretch and walk on the plane. This has not happened before. The marks are not painful to touch and are not raised. I would appreciate your advice.
Thanks