Are Flex / De Rated take offs safe?

[thegreek]

Barit, the link that you posted about FLEX Temp clears up a lot of questions, great !!

But surprised me with this:

"It Increases fuel burn.
Strange, but true. This is because:

1. Assuming an uninterrupted climb, it will take longer to reach the more economical cruise altitude than a full thrust climb.
2. Engines are less efficient when not at full thrust. "