adjustable aerobridge air jetty airbridge aircraft door airport angle board boarding bridge cab connected connecting connection disconnect disconnected disembark disembarking enclosed extend extendable exterior gate gate attendant gateway height high interior jet bridge jetway loading bridge movable movable connector passenger boarding bridge passenger walkway passengers portal retractable retractable tunnel retracted retracting safety security slope sloping terminal walkway across bus coach comfortable empty flowering flowers hi-tech modern movement moving multi-lingual no-passengers on-board-tour-commentary plants railing seating seats silhouette Singapore tourism tourists transport transportation travel traveling travelling