Santa may have his work cut out this year.Demand for toys is at an all-time high.And U.S. suppliers and retailers are racing to outrun severe air, sea and land shipping snarls.The holidays account for a major chunk of the toy industry's nearly $33 billion annual sales.LEGO, L.O.L. Surprise dolls, Barbies and PlayStations were among top sellers last year.But hitches in logistics could result in empty-handed consumers and lost sales for retailers like Walmart and Target.Health worries have hit port operations in key exporters such as Vietnam. Reuters and analysts have seen gaps in shelves among seasonal items.Including school supplies and backpacks, Halloween decor and costumes.Six leading toy makers have said they are using pricey cargo planes, routing shipments to new seaports, and asking retailers like Target to do their own shipping.One expert says the price of cargo flights has more than doubled, and there's little or no capacity left between now and year's end. In the first seven months of 2021, U.S. imports of dolls, toys and games averaged $1.88 billion per month.Up 50% from the same period in 2019.And industry watchers say 2021 is already seeing record demand.Walmart and Target, which have hired their own ships in the scramble to secure goods, did not comment on holiday toy inventories.Mattel in July warned that its supplies were disrupted when the global health crisis hit ports and plants in Asia, worsening shipping container shortages. LEGO said it isn't "experiencing any significant disruption to the overall supply of products" because its factories and distribution centres are close to its markets.