Future Perfect Continuous Tense

Future Perfect Continuous has two different forms: "will have been doing " and "be going to have been doing." Unlike Simple Future forms, Future Perfect Continuous forms are usually interchangeable.

FORM Future Perfect Continuous with "Will"

[will have been + present participle]

Examples:

• You will have been waiting for more than two hours when her plane finally arrives.
• Will you have been waiting for more than two hours when her plane finally arrives?
• You will not have been waiting for more than two hours when her plane finally arrives.

FORM Future Perfect Continuous with "Be Going To"

[am/is/are + going to have been + present participle]

Examples:

• You are going to have been waiting for more than two hours when her plane finally arrives.
• Are you going to have been waiting for more than two hours when her plane finally arrives?
• You are not going to have been waiting for more than two hours when her plane finally arrives.

copied from: english page