My understanding is that since Christ will come "on the clouds" which is the way he left the earth.
While the WT and Bible Student groups continue to hold onto the view that Christ came invisible and quietly and only their group was made aware of it, this is in direct contrary to what the scriptures say;
Matthew 24:30
"At that time the sign of the Son of Man will appear in the sky, and all the nations of the earth will mourn. They will see the Son of Man coming on the clouds of the sky, with power and great glory
Notice also Christ's return is not a quiet one;
Matthew 24:31 And he will send his angels with a loud trumpet call, and they will gather his elect from the four winds, from one end of the heavens to the other.
See also the following verses;
1 Thessalonians 4:16
For the Lord himself will come down from heaven, with a loud command, with the voice of the archangel and with the trumpet call of God, and the dead in Christ will rise first.
Matthew 25:31 "When the Son of Man comes in his glory, and all the angelswithhim, he will sit on his throne in heavenly glory.
Jesus also warns us not to believe it when someone says that he already came;
23 At that time if anyone says to you, 'Look, here is the Christ!' or, 'There he is!' do not believe it. 24 For false Christs and false prophets will appear and perform great signs and miracles to deceive even the elect—if that were possible. 25 See, I have told you ahead of time.
26 "So if anyone tells you, 'There he is, out in the desert,' do not go out; or, 'Here he is, in the inner rooms,' do not believe it. 27 For as lightning that comes from the east is visible even in the west, so will be the coming of the Son of Man.
Peace, Lilly