Step 1: Understanding the Poem:
The poem captures a single poignant moment of parting that evokes larger themes of time, ageing and loss.
Step 2: Central Idea:
It reflects universal anxieties about a parent's mortality, using the mother's aged appearance as a painful reminder of the inevitability of loss, even as the poet tries to reassure herself with a smile.
Final Answer:
The poem reflects on the pain and fear that come with watching a parent age, as the poet's glimpse of her mother's pale, sleeping face during a journey to the airport brings her face-to-face with the reality of eventual loss.