Spirituality is a personnal path. I beleive Morihei Ueshiba created Aikido in harmony with some unusual or 'divine' paterns. It is also a very effective and technical martial art.
Considering this, one could practice Aikido for 30 years without even thinking to the word 'spirituality'. But another one could also find a way to develop his spirituality and getting another part of O-Sensei's teaching.
For example, Saito Sensei had a great Kokyu power, Hikitsuchi Sensei developped the power of Ki; each of them took a part of the founder's teaching. Every Aikido practicioner can express Aikido in the way he understands it.
Aikido is a tool to become who you really are, and spirituality is a tool to help you.
''Know who you are and you'll know your opponent.''
But this a personnal choice, not an obligation.