Mir diamond mine
... that the Mir diamond mine is so large that its natural downward air flow can crash helicopters?
... that the <b id="mwCMo"><a class="mw-redirect" href="./Mir_Mine" id="mwCMs" rel="mw:WikiLink" title="Mir Mine">Mir diamond mine</a></b> is so large that its natural <a href="./Vertical_draft" id="mwCMw" rel="mw:WikiLink" title="Vertical draft">downward air flow</a> can crash helicopters?