aircraft anchored balloon cable checks circular colors colours control controlled duty-pilot engineers fabric filled flight-operation gondola height helium helium-balloon high inspected inspections large limited mesh metal-cable metal-line monitored monitoring motion movement net passengers pilot piloted registered ride safe safety secure secured sights sightseeing Singapore tethered tourists views weather-limits wind-limits against the ceiling attached balloons blown-up blue bright bunched colorful colourful dark dark blue decorations helium filled inflated interior light lighter than air red reflection rounded rubber strings textures accessory anniversary appreciation birthday brown celebrate celebrating celebration celebratory decorated decorative fiftieth fifty floating foliage fun garden gas-filled gold golden happiness happy helium-filled leaves plants preparation prepare prepared round shade shaded shadows shrubbery shrubs special specific thankfulness