I've had many similar experiences tracking military aircraft. Many flights are "secret" in that they really don't want you to know who they are or what they are doing. Some make up call signs, aircraft type and id. Or, they are simply listed as n/a with a very short, fat aircraft symbol. Pay attention to the ones that orbit in the same way the P8's do rather than just flying from A to B.
I've had many similar experiences tracking military aircraft. Many flights are "secret" in that they really don't want you to know who they are or what they are doing. Some make up call signs, aircraft type and id. Or, they are simply listed as n/a with a very short, fat aircraft symbol. Pay attention to the ones that orbit in the same way the P8's do rather than just flying from A to B.