MADRID, April 29 (Reuters) - Spanish electricity grid

operator Red Electrica said it was able to supply

99.16% of the country's electricity demand early on Tuesday as

the system gradually recovers from a nationwide blackout on

Monday.

All the country's substations were operating on Tuesday

morning, Red Electrica said in a post on X social media. "We

keep working on restoring (power)," it added.

A huge power outage hit most of the Iberian Peninsula on

Monday morning, bringing both Spain and Portugal to a standstill

- grounding planes, halting public transportation and forcing

hospitals to restrict routine proceedings.