def is_altitude(value: str) -> bool:
    """Returns True if the value is a possible altitude"""
    if len(value) < 5:
        return False
    if value[:4] == "SFC/":
        return True
    if value[:2] == "FL" and value[2:5].isdigit():
        return True
    first, *_ = value.split("/")
    if first[-2:] == "FT" and first[-5:-2].isdigit():
        return True
    return False