What is an omen?
An omen is an event or happening that you take as sign of something to come
The Ship's cat
On the Titanic, they had a cat. The cat who had just happened to have a litter of kittens abandoned the Titanic before it set sail. She even took the time to remove each kitten one by one. A stoker aboard took this as a bad omen and felt a little nervous being aboard.

The ship colliding
Just before leaving South Hampton Harbor, the Titanic collided with a ship ironically named New York. Some saw this as a bad omen set out to warn people.

The Comatose girl
There was a dying girl in England who was in a state of unconsciousness or in a comatose. She was under close eye by her doctor. The girl suddenly opened her eyes and said "I see a big ship sinking. Oh, mister can't you? The people in the water and old Wally and his fiddle.
The girl later died that night. It was the next morning that the doctor heard of the Titanic disaster, and he also learned that his friend Wallace Harley, or Wally had died in the tragedy.

"BRUCE IS IN TROUBLE!"
Bruce Ismay's brother's grandson was in a coma on the night of the Titanic tragedy. He had miraculously come out of the coma around the same time as the Titanic was said to go down. He yelled "Bruce is in trouble! Bruce is in trouble!"

Questionable
As passengers boarded, they were shocked to see a figure popping out of the smoke stack. The figure was completely black. The figure was actually popping out of the dummy smoke stack; no passengers knew that that smoke stack wasn't real. The figure was actually a stoker covered with the black coal. The passengers say that they saw the figure as being death himself. An omen, indeed...

The bottle
It is an old tradition to christen the ships before their maiden voyage. They do this by throwing a bottle of liquid onto the ship. If the bottle breaks than it is bad luck, and vice versa if it doesn't. The Titanic however, was not successfully christened, the bottle did not break. This is seen as a HUGE bad omen.

The Rat
On the night of the Titanic tragedy, before that it was noticed that the ship was sinking, third class passengers were having a dance party. A giant rat made its appearance. The men tried to catch the rat but were unable to do so. Many third class passengers saw this as an omen of something bad to come.

The Hull Number
Titanic hull number happened to be 390904 and its mirror image happened to be an image similar to the words "no pope". This was taken to those who were Catholic as a MAJOR bad omen.

Sealed
While under construction in Belfast, a worker was accidently sealed into Titanic's hull. This was seen as a bad omen.

The Big Sister
The same captain that commanded the Titanic, Captain Smith, was also the captain of the Titanic sister ship, the Olympic. The Olympics’ maiden voyage was June, 21, 1911 from South Hampton to New York, same as Titanic. The journey was successful but there was one small problem. When they arrived at the New York Harbor, they had 12 tug boats pulling it in. One tug boat happened to get caught up in the ropes and it span around and crashed into the Olympic. It than became trapped under the stern. Luckily, the tug boat was freed. This was seen as an omen

There were people who felt something inside than made them uneasy. Such as Henry B. Harris, a theatre producer, his business felt a real scene of doom. He told Henry to cancel, but it was too late. There was a man named Major Archibald Butt, Military guide to President William Howard Talt. He wrote on a letter to his sister in law reading "if the ship goes down, you'll find my affairs in ship shape”. Chief officer Wilde wrote to his sister "I still don't like this ship... I have a queer feeling about it. Eva Hart's mother, Ester, felt an emending disaster would happen in the night. She would sleep in the day and knit and read in the night. There were others that saw a disaster in their dreams such as John Humes's mother. Humes was 1 of the 8 man band on the titanic. His mother dreamt something would happen and begged him to stay, he died in the tragedy.